diff --git a/Lombiq.HelpfulExtensions/Controllers/ContentSetController.cs b/Lombiq.HelpfulExtensions/Controllers/ContentSetController.cs
new file mode 100644
index 00000000..03b929c7
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Controllers/ContentSetController.cs
@@ -0,0 +1,25 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Services;
+using Microsoft.AspNetCore.Mvc;
+using OrchardCore;
+using OrchardCore.Modules;
+using System.Threading.Tasks;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Controllers;
+
+[Feature(FeatureIds.ContentSets)]
+public class ContentSetController : Controller
+{
+    private readonly IContentSetManager _contentSetManager;
+    private readonly IOrchardHelper _orchardHelper;
+
+    public ContentSetController(IContentSetManager contentSetManager, IOrchardHelper orchardHelper)
+    {
+        _contentSetManager = contentSetManager;
+        _orchardHelper = orchardHelper;
+    }
+
+    public async Task<IActionResult> Create(string fromContentItemId, string fromPartName, string newKey) =>
+        await _contentSetManager.CloneContentItemAsync(fromContentItemId, fromPartName, newKey) is { } content
+            ? Redirect(_orchardHelper.GetItemEditUrl(content))
+            : NotFound();
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Drivers/ContentSetPartDisplayDriver.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Drivers/ContentSetPartDisplayDriver.cs
new file mode 100644
index 00000000..90f80478
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Drivers/ContentSetPartDisplayDriver.cs
@@ -0,0 +1,132 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Events;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Services;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels;
+using Lombiq.HelpfulLibraries.OrchardCore.Contents;
+using Microsoft.Extensions.Localization;
+using OrchardCore.ContentManagement;
+using OrchardCore.ContentManagement.Display.ContentDisplay;
+using OrchardCore.ContentManagement.Display.Models;
+using OrchardCore.ContentManagement.Metadata.Models;
+using OrchardCore.DisplayManagement.ModelBinding;
+using OrchardCore.DisplayManagement.Views;
+using OrchardCore.Entities;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Drivers;
+
+public class ContentSetPartDisplayDriver : ContentPartDisplayDriver<ContentSetPart>
+{
+    private const string ShapeType = $"{nameof(ContentSetPart)}_{CommonContentDisplayTypes.SummaryAdmin}";
+
+    private readonly IContentSetManager _contentSetManager;
+    private readonly IIdGenerator _idGenerator;
+    private readonly IEnumerable<IContentSetEventHandler> _contentSetEventHandlers;
+    private readonly IStringLocalizer<ContentSetPartDisplayDriver> T;
+
+    public ContentSetPartDisplayDriver(
+        IContentSetManager contentSetManager,
+        IIdGenerator idGenerator,
+        IEnumerable<IContentSetEventHandler> contentSetEventHandlers,
+        IStringLocalizer<ContentSetPartDisplayDriver> stringLocalizer)
+    {
+        _contentSetManager = contentSetManager;
+        _idGenerator = idGenerator;
+        _contentSetEventHandlers = contentSetEventHandlers;
+        T = stringLocalizer;
+    }
+
+    public override IDisplayResult Display(ContentSetPart part, BuildPartDisplayContext context) =>
+        Combine(
+            Initialize<ContentSetPartViewModel>(
+                    $"{ShapeType}_Tags",
+                    model => BuildViewModelAsync(model, part, context.TypePartDefinition, isNew: false))
+                .Location(CommonContentDisplayTypes.SummaryAdmin, "Tags:11"),
+            Initialize<ContentSetPartViewModel>(
+                    $"{ShapeType}_Links",
+                    model => BuildViewModelAsync(model, part, context.TypePartDefinition, isNew: false))
+                .Location(CommonContentDisplayTypes.SummaryAdmin, "Actions:5")
+        );
+
+    public override IDisplayResult Edit(ContentSetPart part, BuildPartEditorContext context) =>
+        Initialize<ContentSetPartViewModel>(
+                $"{nameof(ContentSetPart)}_Edit",
+                model => BuildViewModelAsync(model, part, context.TypePartDefinition, context.IsNew))
+            .Location($"Parts:0%{context.TypePartDefinition.Name};0");
+
+    public override async Task<IDisplayResult> UpdateAsync(
+        ContentSetPart part,
+        IUpdateModel updater,
+        UpdatePartEditorContext context)
+    {
+        var viewModel = new ContentSetPartViewModel();
+
+        if (await updater.TryUpdateModelAsync(viewModel, Prefix))
+        {
+            part.Key = viewModel.Key;
+
+            // Need to do this here to support displaying the message to save before adding when the
+            // item has not been saved yet.
+            if (string.IsNullOrEmpty(part.ContentSet))
+            {
+                part.ContentSet = _idGenerator.GenerateUniqueId();
+            }
+        }
+
+        return await EditAsync(part, context);
+    }
+
+    public async ValueTask BuildViewModelAsync(
+        ContentSetPartViewModel model,
+        ContentSetPart part,
+        ContentTypePartDefinition definition,
+        bool isNew)
+    {
+        model.Key = part.Key;
+        model.ContentSet = part.ContentSet;
+        model.ContentSetPart = part;
+        model.Definition = definition;
+        model.IsNew = isNew;
+
+        var existingContentItems = (await _contentSetManager.GetContentItemsAsync(part.ContentSet))
+            .ToDictionary(item => item.Get<ContentSetPart>(definition.Name)?.Key);
+
+        var options = new Dictionary<string, ContentSetLinkViewModel>
+        {
+            [ContentSetPart.Default] = new(
+                IsDeleted: false,
+                T["Default content item"],
+                existingContentItems.GetMaybe(ContentSetPart.Default)?.ContentItemId,
+                ContentSetPart.Default),
+        };
+
+        var supportedOptions = (await _contentSetEventHandlers.AwaitEachAsync(item => item.GetSupportedOptionsAsync(part, definition)))
+            .SelectMany(links => links ?? Enumerable.Empty<ContentSetLinkViewModel>());
+        options.AddRange(supportedOptions, link => link.Key);
+
+        // Ensure the existing content item IDs are applied to the supported option links.
+        existingContentItems
+            .Where(pair => options.GetMaybe(pair.Key)?.ContentItemId != pair.Value.ContentItemId)
+            .ForEach(pair => options[pair.Key] = options[pair.Key] with { ContentItemId = pair.Value.ContentItemId });
+
+        // Content items that have been added to the set but no longer generate a valid option matching their key.
+        var inapplicableSetMembers = existingContentItems
+            .Where(pair => !options.ContainsKey(pair.Key))
+            .Select(pair => new ContentSetLinkViewModel(
+                IsDeleted: true,
+                T["{0} (No longer applicable)", pair.Value.DisplayText].Value,
+                pair.Value.ContentItemId,
+                pair.Key));
+        options.AddRange(inapplicableSetMembers, link => link.Key);
+
+        model.MemberLinks = options
+            .Values
+            .Where(link => link.Key != model.Key && link.ContentItemId != part.ContentItem.ContentItemId)
+            .OrderBy(link => string.IsNullOrEmpty(link.ContentItemId) ? 1 : 0)
+            .ThenBy(link => link.IsDeleted ? 1 : 0)
+            .ThenBy(link => link.DisplayText)
+            .ToList();
+    }
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Events/IContentSetEventHandler.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Events/IContentSetEventHandler.cs
new file mode 100644
index 00000000..7f17b8d9
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Events/IContentSetEventHandler.cs
@@ -0,0 +1,43 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels;
+using OrchardCore.ContentManagement;
+using OrchardCore.ContentManagement.Metadata.Models;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Events;
+
+/// <summary>
+/// Events relating to <see cref="ContentSetPart"/> containing content items.
+/// </summary>
+public interface IContentSetEventHandler
+{
+    /// <summary>
+    /// Returns the available items relating to the content item that contains the <paramref name="part"/>. This can be
+    /// used for a dropdown to access the other contents in the set.
+    /// </summary>
+    /// <returns>
+    /// A collection of option links, or <see langword="null"/> if this even handler is not applicable for the <paramref
+    /// name="part"/>.
+    /// </returns>
+    Task<IEnumerable<ContentSetLinkViewModel>> GetSupportedOptionsAsync(
+        ContentSetPart part,
+        ContentTypePartDefinition definition) =>
+        Task.FromResult<IEnumerable<ContentSetLinkViewModel>>(null);
+
+    /// <summary>
+    /// The event triggered when a donor content item is cloned but before it's published.
+    /// </summary>
+    /// <param name="content">The new content item.</param>
+    /// <param name="definition">
+    /// The part definition indicating which <see cref="ContentSetPart"/> is responsible for this event.
+    /// </param>
+    /// <param name="contentSet">The unique ID of the content set.</param>
+    /// <param name="newKey">The new item's key, which is unique within the content set.</param>
+    Task CreatingAsync(
+        ContentItem content,
+        ContentTypePartDefinition definition,
+        string contentSet,
+        string newKey) =>
+        Task.CompletedTask;
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Indexes/ContentSetIndex.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Indexes/ContentSetIndex.cs
new file mode 100644
index 00000000..b03fe52b
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Indexes/ContentSetIndex.cs
@@ -0,0 +1,56 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Microsoft.Extensions.DependencyInjection;
+using OrchardCore.ContentManagement;
+using OrchardCore.ContentManagement.Metadata;
+using System;
+using System.Linq;
+using YesSql.Indexes;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Indexes;
+
+public class ContentSetIndex : MapIndex
+{
+    public string ContentItemId { get; set; }
+    public string PartName { get; set; }
+    public bool IsPublished { get; set; }
+    public string ContentSet { get; set; }
+    public string Key { get; set; }
+
+    public static ContentSetIndex FromPart(ContentSetPart part, string partName) =>
+        new()
+        {
+            ContentItemId = part.ContentItem.ContentItemId,
+            PartName = partName,
+            IsPublished = part.ContentItem.Published,
+            ContentSet = part.ContentSet,
+            Key = part.Key,
+        };
+}
+
+public class ContentSetIndexProvider : IndexProvider<ContentItem>
+{
+    private readonly IServiceProvider _provider;
+
+    // We can't inject Lazy<IContentDefinitionManager> because it will throw a "Cannot resolve scoped service
+    // 'OrchardCore.ContentManagement.Metadata.IContentDefinitionManager' from root provider." exception.
+    public ContentSetIndexProvider(IServiceProvider provider) =>
+        _provider = provider;
+
+    public override void Describe(DescribeContext<ContentItem> context) =>
+        context.For<ContentSetIndex>().Map(contentItem =>
+        {
+            if (!contentItem.Latest) return Enumerable.Empty<ContentSetIndex>();
+
+            using var scope = _provider.CreateScope();
+            var contentDefinitionManager = scope.ServiceProvider.GetRequiredService<IContentDefinitionManager>();
+
+            return contentDefinitionManager
+                .GetTypeDefinition(contentItem.ContentType)
+                .Parts
+                .Where(part => part.PartDefinition.Name == nameof(ContentSetPart))
+                .Select(part => new { Part = contentItem.Get<ContentSetPart>(part.Name), part.Name })
+                .Where(info => info.Part != null)
+                .Select(info => ContentSetIndex.FromPart(info.Part, info.Name))
+                .Where(index => index.ContentSet != null);
+        });
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Migrations.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Migrations.cs
new file mode 100644
index 00000000..1c8364a7
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Migrations.cs
@@ -0,0 +1,34 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Indexes;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Lombiq.HelpfulLibraries.OrchardCore.Data;
+using OrchardCore.ContentManagement.Metadata;
+using OrchardCore.ContentManagement.Metadata.Settings;
+using OrchardCore.Data.Migration;
+using YesSql.Sql;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets;
+
+public class Migrations : DataMigration
+{
+    private readonly IContentDefinitionManager _contentDefinitionManager;
+
+    public Migrations(IContentDefinitionManager contentDefinitionManager) =>
+        _contentDefinitionManager = contentDefinitionManager;
+
+    public int Create()
+    {
+        _contentDefinitionManager.AlterPartDefinition(nameof(ContentSetPart), builder => builder
+            .Attachable()
+            .Reusable()
+            .WithDisplayName("Content Set"));
+
+        SchemaBuilder.CreateMapIndexTable<ContentSetIndex>(table => table
+            .Column<string>(nameof(ContentSetIndex.ContentItemId), column => column.WithCommonUniqueIdLength())
+            .Column<string>(nameof(ContentSetIndex.PartName))
+            .Column<bool>(nameof(ContentSetIndex.IsPublished))
+            .Column<string>(nameof(ContentSetIndex.ContentSet))
+            .Column<string>(nameof(ContentSetIndex.Key)));
+
+        return 1;
+    }
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Models/ContentSetPart.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Models/ContentSetPart.cs
new file mode 100644
index 00000000..d5bd47ae
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Models/ContentSetPart.cs
@@ -0,0 +1,15 @@
+using OrchardCore.ContentManagement;
+using System.Text.Json.Serialization;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+
+public class ContentSetPart : ContentPart
+{
+    public const string Default = nameof(Default);
+
+    public string ContentSet { get; set; }
+    public string Key { get; set; } = Default;
+
+    [JsonIgnore]
+    public bool IsDefault => Key == Default;
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/ContentSetManager.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/ContentSetManager.cs
new file mode 100644
index 00000000..5145175d
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/ContentSetManager.cs
@@ -0,0 +1,74 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Events;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Indexes;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using OrchardCore.ContentManagement;
+using OrchardCore.ContentManagement.Metadata;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using YesSql;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Services;
+
+public class ContentSetManager : IContentSetManager
+{
+    private readonly IContentDefinitionManager _contentDefinitionManager;
+    private readonly IContentManager _contentManager;
+    private readonly IEnumerable<IContentSetEventHandler> _contentSetEventHandlers;
+    private readonly ISession _session;
+
+    public ContentSetManager(
+        IContentDefinitionManager contentDefinitionManager,
+        IContentManager contentManager,
+        IEnumerable<IContentSetEventHandler> contentSetEventHandlers,
+        ISession session)
+    {
+        _contentDefinitionManager = contentDefinitionManager;
+        _contentManager = contentManager;
+        _contentSetEventHandlers = contentSetEventHandlers;
+        _session = session;
+    }
+
+    public Task<IEnumerable<ContentSetIndex>> GetIndexAsync(string setId) =>
+        _session.QueryIndex<ContentSetIndex>(index => index.ContentSet == setId).ListAsync();
+
+    public async Task<IEnumerable<ContentItem>> GetContentItemsAsync(string setId) =>
+        await _contentManager.GetAsync((await GetIndexAsync(setId)).Select(index => index.ContentItemId));
+
+    public async Task<ContentItem> CloneContentItemAsync(string fromContentItemId, string fromPartName, string newKey)
+    {
+        if (string.IsNullOrEmpty(fromPartName)) fromPartName = nameof(ContentSetPart);
+
+        if (await _contentManager.GetAsync(fromContentItemId) is not { } original ||
+            original.Get<ContentSetPart>(fromPartName)?.ContentSet is not { } contentSet ||
+            await _contentManager.CloneAsync(original) is not { } content)
+        {
+            return null;
+        }
+
+        var exists = await _session
+            .QueryIndex<ContentSetIndex>(index => index.ContentSet == contentSet && index.Key == newKey)
+            .FirstOrDefaultAsync() is not null;
+        if (exists) throw new InvalidOperationException($"The key \"{newKey}\" already exists for the content set \"{contentSet}\".");
+
+        content.Alter<ContentSetPart>(fromPartName, part =>
+        {
+            part.ContentSet = contentSet;
+            part.Key = newKey;
+        });
+
+        var contentTypePartDefinition = _contentDefinitionManager
+            .GetTypeDefinition(content.ContentType)
+            .Parts
+            .Single(definition => definition.Name == fromPartName);
+
+        foreach (var handler in _contentSetEventHandlers)
+        {
+            await handler.CreatingAsync(content, contentTypePartDefinition, contentSet, newKey);
+        }
+
+        await _contentManager.PublishAsync(content);
+        return content;
+    }
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/IContentSetManager.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/IContentSetManager.cs
new file mode 100644
index 00000000..ff95f6a6
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Services/IContentSetManager.cs
@@ -0,0 +1,35 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Indexes;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using OrchardCore.ContentManagement;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.Services;
+
+/// <summary>
+/// A service for getting and setting content sets.
+/// </summary>
+public interface IContentSetManager
+{
+    /// <summary>
+    /// Returns all <see cref="ContentSetIndex"/> entries for the content set with the given <paramref name="setId"/>.
+    /// </summary>
+    Task<IEnumerable<ContentSetIndex>> GetIndexAsync(string setId);
+
+    /// <summary>
+    /// Returns all content items in a content set with the given <paramref name="setId"/>.
+    /// </summary>
+    Task<IEnumerable<ContentItem>> GetContentItemsAsync(string setId);
+
+    /// <summary>
+    /// Creates and publishes a new content item in the same content set by cloning the one with the given ID.
+    /// </summary>
+    /// <param name="fromContentItemId">The content item ID of the content to be cloned.</param>
+    /// <param name="fromPartName">
+    /// The name of the <see cref="ContentSetPart"/> whose set has to be amended. If it's not a named content part, then
+    /// it can be <see langword="null"/>.
+    /// </param>
+    /// <param name="newKey">The new key of the content set item, must be unique within the set..</param>
+    /// <returns>The newly created content item, or <see langword="null"/> if the source was not found.</returns>
+    Task<ContentItem> CloneContentItemAsync(string fromContentItemId, string fromPartName, string newKey);
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/Startup.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Startup.cs
new file mode 100644
index 00000000..4a5f3d97
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/Startup.cs
@@ -0,0 +1,33 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Drivers;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Indexes;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Services;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.DependencyInjection;
+using OrchardCore.ContentManagement;
+using OrchardCore.ContentManagement.Display.ContentDisplay;
+using OrchardCore.Modules;
+using System;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets;
+
+[Feature(FeatureIds.ContentSets)]
+public class Startup : StartupBase
+{
+    public override void ConfigureServices(IServiceCollection services)
+    {
+        services
+            .AddContentPart<ContentSetPart>()
+            .UseDisplayDriver<ContentSetPartDisplayDriver>()
+            .WithIndex<ContentSetIndexProvider>()
+            .WithMigration<Migrations>();
+
+        services.AddScoped<IContentSetManager, ContentSetManager>();
+    }
+
+    public override void Configure(IApplicationBuilder app, IEndpointRouteBuilder routes, IServiceProvider serviceProvider)
+    {
+        // No need for anything here yet.
+    }
+}
diff --git a/Lombiq.HelpfulExtensions/Extensions/ContentSets/ViewModels/ContentSetPartViewModel.cs b/Lombiq.HelpfulExtensions/Extensions/ContentSets/ViewModels/ContentSetPartViewModel.cs
new file mode 100644
index 00000000..f97b3cbb
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Extensions/ContentSets/ViewModels/ContentSetPartViewModel.cs
@@ -0,0 +1,27 @@
+using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using OrchardCore.ContentManagement.Metadata.Models;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels;
+
+public class ContentSetPartViewModel
+{
+    public string ContentSet { get; set; }
+    public string Key { get; set; }
+
+    [BindNever]
+    public ContentTypePartDefinition Definition { get; set; }
+
+    [BindNever]
+    public ContentSetPart ContentSetPart { get; set; }
+
+    [BindNever]
+    public IEnumerable<ContentSetLinkViewModel> MemberLinks { get; set; } = Enumerable.Empty<ContentSetLinkViewModel>();
+
+    [BindNever]
+    public bool IsNew { get; set; }
+}
+
+public record ContentSetLinkViewModel(bool IsDeleted, string DisplayText, string ContentItemId, string Key);
diff --git a/Lombiq.HelpfulExtensions/FeatureIds.cs b/Lombiq.HelpfulExtensions/FeatureIds.cs
index ff5e584f..3cd3b3ee 100644
--- a/Lombiq.HelpfulExtensions/FeatureIds.cs
+++ b/Lombiq.HelpfulExtensions/FeatureIds.cs
@@ -6,6 +6,7 @@ public static class FeatureIds
     private const string FeatureIdPrefix = Base + ".";
 
     public const string CodeGeneration = FeatureIdPrefix + nameof(CodeGeneration);
+    public const string ContentSets = FeatureIdPrefix + nameof(ContentSets);
     public const string ContentTypes = FeatureIdPrefix + nameof(ContentTypes);
     public const string Flows = FeatureIdPrefix + nameof(Flows);
     public const string ShapeTracing = FeatureIdPrefix + nameof(ShapeTracing);
diff --git a/Lombiq.HelpfulExtensions/Manifest.cs b/Lombiq.HelpfulExtensions/Manifest.cs
index b2b6d021..b59ef142 100644
--- a/Lombiq.HelpfulExtensions/Manifest.cs
+++ b/Lombiq.HelpfulExtensions/Manifest.cs
@@ -19,6 +19,17 @@
     }
 )]
 
+[assembly: Feature(
+    Id = ContentSets,
+    Name = "Lombiq Helpful Extensions - Content Sets",
+    Category = "Development",
+    Description = "Create arbitrary collections of content items.",
+    Dependencies = new[]
+    {
+        "OrchardCore.ContentManagement",
+    }
+)]
+
 [assembly: Feature(
     Id = Flows,
     Name = "Lombiq Helpful Extensions - Flows Helpful Extensions",
diff --git a/Lombiq.HelpfulExtensions/Views/ContentSetPart.Edit.cshtml b/Lombiq.HelpfulExtensions/Views/ContentSetPart.Edit.cshtml
new file mode 100644
index 00000000..9fb2805b
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Views/ContentSetPart.Edit.cshtml
@@ -0,0 +1,21 @@
+@model Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels.ContentSetPartViewModel
+
+<p>@T["Information about the \"{0}\" content set part.", Model.Definition.Name]</p>
+
+<fieldset asp-for="Key" label="@T["Key"]" readonly="true"></fieldset>
+
+@if (!Model.IsNew)
+{
+    <fieldset class="form-group mb-3 col-xl-6">
+        <label>@T["Other members of this content set"]</label>
+        <ul>
+            @foreach (var link in Model.MemberLinks)
+            {
+                <shape type="ContentSetPart_MemberLink"
+                       prop-Link="@link"
+                       prop-ContentSetPart="@Model.ContentSetPart"
+                       prop-Definition="@Model.Definition"></shape>
+            }
+        </ul>
+    </fieldset>
+}
diff --git a/Lombiq.HelpfulExtensions/Views/ContentSetPart.MemberLink.cshtml b/Lombiq.HelpfulExtensions/Views/ContentSetPart.MemberLink.cshtml
new file mode 100644
index 00000000..154a5d59
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Views/ContentSetPart.MemberLink.cshtml
@@ -0,0 +1,32 @@
+@using OrchardCore
+@using OrchardCore.ContentManagement.Metadata.Models
+@using OrchardCore.Contents.Controllers
+@using Lombiq.HelpfulExtensions.Extensions.ContentSets.Controllers
+@using Lombiq.HelpfulExtensions.Extensions.ContentSets.Models
+@using Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels
+@{
+    if (Model.Link is not ContentSetLinkViewModel link) { return; }
+    var contentSetPart = Model.ContentSetPart as ContentSetPart;
+    var definition = Model.Definition as ContentTypePartDefinition;
+}
+
+<li>
+    @if (!string.IsNullOrEmpty(link.ContentItemId))
+    {
+        var url = Orchard.Action<AdminController>(controller => controller.Edit(
+            link.ContentItemId));
+        <a class="dropdown-item btn-sm" href="@url" title=@T["Edit {0}", link.DisplayText]>
+            <i class="fa-solid fa-edit" aria-hidden="true"></i> @link.DisplayText
+        </a>
+    }
+    else
+    {
+        var url = Orchard.Action<ContentSetController>(controller => controller.Create(
+            contentSetPart.ContentItem.ContentItemId,
+            definition.Name,
+            link.Key));
+        <a class="dropdown-item btn-sm" href="@url" title=@T["Create {0}", link.DisplayText]>
+            <i class="fa-solid fa-plus" aria-hidden="true"></i> @link.DisplayText
+        </a>
+    }
+</li>
diff --git a/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Links.cshtml b/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Links.cshtml
new file mode 100644
index 00000000..538a906b
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Links.cshtml
@@ -0,0 +1,26 @@
+@model Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels.ContentSetPartViewModel
+
+@{
+    if (string.IsNullOrEmpty(Model.ContentSet) || !Model.MemberLinks.Any()) { return; }
+
+    var title = T[Model.Definition.Name];
+}
+
+<div class="btn-group" title="@title">
+    <button type="button"
+            class="btn btn-sm btn-info dropdown-toggle localizations"
+            data-bs-toggle="dropdown"
+            aria-haspopup="true"
+            aria-expanded="false">
+        <span>@title</span>
+    </button>
+    <ul class="dropdown-menu dropdown-menu-end">
+        @foreach (var link in Model.MemberLinks)
+        {
+            <shape type="ContentSetPart_MemberLink"
+                   prop-link="@link"
+                   prop-ContentSetPart="@Model.ContentSetPart"
+                   prop-Definition="@Model.Definition"></shape>
+        }
+    </ul>
+</div>
diff --git a/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Tags.cshtml b/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Tags.cshtml
new file mode 100644
index 00000000..1f35651d
--- /dev/null
+++ b/Lombiq.HelpfulExtensions/Views/ContentSetPart.SummaryAdmin.Tags.cshtml
@@ -0,0 +1,9 @@
+@model Lombiq.HelpfulExtensions.Extensions.ContentSets.ViewModels.ContentSetPartViewModel
+
+@if (Model.ContentSetPart.Key != null)
+{
+    <span class="badge ta-badge font-weight-normal" data-bs-toggle="tooltip" title="@T[Model.Definition.Name]">
+        <i class="fa-solid fa-ellipsis" aria-hidden="true"></i>
+        @T[Model.Definition.Name]: @Model.ContentSetPart.Key
+    </span>
+}