Here is prototype of a form builder created with Blazor WebAssembly:
https://alexeyboiko.github.io/FormDesignerDemo/
Chech out "How to: Blazor WebAssembly: dynamic creation of components based on JSON configuration":
https://alexey-boyko.medium.com/blazor-webassembly-dynamic-creation-of-components-based-on-json-configuration-d1df664e5e19