diff --git a/Model/Processor/ImportProcessor.php b/Model/Processor/ImportProcessor.php
index 56ac276..c7730f6 100644
--- a/Model/Processor/ImportProcessor.php
+++ b/Model/Processor/ImportProcessor.php
@@ -119,6 +119,12 @@ public function process()
                         continue;
                     }
 
+                    if ($this->shouldSkipConfig($configPath, $scopeType, $scopeId, $value)) {
+                        $this->getOutput()->writeln(sprintf('<comment>[%s] [%s] %s => %s</comment>', $scopeType, $scopeId, $configPath, 'SKIPPED'));
+
+                        continue;
+                    }
+
                     $this->configWriter->save($configPath, $value, $scopeType, $scopeId);
                     $this->getOutput()->writeln(sprintf('<comment>[%s] [%s] %s => %s</comment>', $scopeType, $scopeId, $configPath, $value));
                 }
@@ -126,6 +132,24 @@ public function process()
         }
     }
 
+    /**
+     * @param string $configPath
+     * @param string $scopeType
+     * @param int $scopeId
+     * @param mixed $value
+     *
+     * @return bool
+     */
+    private function shouldSkipConfig($configPath, $scopeType, $scopeId, $value)
+    {
+        if (is_array($value) && (isset($value['if-not-set']) || (isset($value['if']) && $value['if'] === 'not-set'))) {
+            $existingValue = $this->configWriter->get($configPath, $scopeType, $scopeId);
+            return $existingValue !== null;
+        }
+
+        return false;
+    }
+
     /**
      * @param array $files
      *
diff --git a/Test/Unit/Model/Processor/ImportProcessorTest.php b/Test/Unit/Model/Processor/ImportProcessorTest.php
index c54362a..d9bdd9a 100644
--- a/Test/Unit/Model/Processor/ImportProcessorTest.php
+++ b/Test/Unit/Model/Processor/ImportProcessorTest.php
@@ -157,4 +157,152 @@ public function process(): void
         $processor->setReader($readerMock);
         $processor->process();
     }
+
+    /**
+     * @test
+     */
+    public function processWithIfNotSetModifier(): void
+    {
+        $finderMock = $this->getMockBuilder(Finder::class)
+            ->onlyMethods(['find'])
+            ->getMock();
+        $finderMock->expects($this->once())->method('find')->willReturn(['abc.yaml']);
+
+        $parseResult = [
+            'test/config/custom_field_if_not_set' => [
+                'default' => [
+                    0 => [
+                        'if-not-set' => true,
+                        'default' => 1,
+                    ],
+                ],
+            ],
+        ];
+
+        $readerMock = $this->getMockBuilder(YamlReader::class)
+            ->onlyMethods(['parse'])
+            ->getMock();
+        $readerMock->expects($this->once())->method('parse')->willReturn($parseResult);
+
+        $this->scopeValidatorMock->expects($this->once())->method('validate')->willReturn(true);
+        $this->configWriterMock->expects($this->once())->method('save');
+        $this->configWriterMock->expects($this->once())->method('get')->willReturn(null);
+
+        $processor = new ImportProcessor($this->configWriterMock, $this->scopeValidatorMock, $this->scopeConverterMock, []);
+        $processor->setOutput($this->outputMock);
+        $processor->setFinder($finderMock);
+        $processor->setReader($readerMock);
+        $processor->process();
+    }
+
+    /**
+     * @test
+     */
+    public function processWithIfNotSetModifierAndExistingValue(): void
+    {
+        $finderMock = $this->getMockBuilder(Finder::class)
+            ->onlyMethods(['find'])
+            ->getMock();
+        $finderMock->expects($this->once())->method('find')->willReturn(['abc.yaml']);
+
+        $parseResult = [
+            'test/config/custom_field_if_not_set' => [
+                'default' => [
+                    0 => [
+                        'if-not-set' => true,
+                        'default' => 1,
+                    ],
+                ],
+            ],
+        ];
+
+        $readerMock = $this->getMockBuilder(YamlReader::class)
+            ->onlyMethods(['parse'])
+            ->getMock();
+        $readerMock->expects($this->once())->method('parse')->willReturn($parseResult);
+
+        $this->scopeValidatorMock->expects($this->once())->method('validate')->willReturn(true);
+        $this->configWriterMock->expects($this->never())->method('save');
+        $this->configWriterMock->expects($this->once())->method('get')->willReturn('existing_value');
+
+        $processor = new ImportProcessor($this->configWriterMock, $this->scopeValidatorMock, $this->scopeConverterMock, []);
+        $processor->setOutput($this->outputMock);
+        $processor->setFinder($finderMock);
+        $processor->setReader($readerMock);
+        $processor->process();
+    }
+
+    /**
+     * @test
+     */
+    public function processWithIfNotSetModifierAlternativeSyntax(): void
+    {
+        $finderMock = $this->getMockBuilder(Finder::class)
+            ->onlyMethods(['find'])
+            ->getMock();
+        $finderMock->expects($this->once())->method('find')->willReturn(['abc.yaml']);
+
+        $parseResult = [
+            'test/config/custom_field_if_not_set' => [
+                'default' => [
+                    0 => [
+                        'if' => 'not-set',
+                        'default' => 1,
+                    ],
+                ],
+            ],
+        ];
+
+        $readerMock = $this->getMockBuilder(YamlReader::class)
+            ->onlyMethods(['parse'])
+            ->getMock();
+        $readerMock->expects($this->once())->method('parse')->willReturn($parseResult);
+
+        $this->scopeValidatorMock->expects($this->once())->method('validate')->willReturn(true);
+        $this->configWriterMock->expects($this->once())->method('save');
+        $this->configWriterMock->expects($this->once())->method('get')->willReturn(null);
+
+        $processor = new ImportProcessor($this->configWriterMock, $this->scopeValidatorMock, $this->scopeConverterMock, []);
+        $processor->setOutput($this->outputMock);
+        $processor->setFinder($finderMock);
+        $processor->setReader($readerMock);
+        $processor->process();
+    }
+
+    /**
+     * @test
+     */
+    public function processWithIfNotSetModifierAlternativeSyntaxAndExistingValue(): void
+    {
+        $finderMock = $this->getMockBuilder(Finder::class)
+            ->onlyMethods(['find'])
+            ->getMock();
+        $finderMock->expects($this->once())->method('find')->willReturn(['abc.yaml']);
+
+        $parseResult = [
+            'test/config/custom_field_if_not_set' => [
+                'default' => [
+                    0 => [
+                        'if' => 'not-set',
+                        'default' => 1,
+                    ],
+                ],
+            ],
+        ];
+
+        $readerMock = $this->getMockBuilder(YamlReader::class)
+            ->onlyMethods(['parse'])
+            ->getMock();
+        $readerMock->expects($this->once())->method('parse')->willReturn($parseResult);
+
+        $this->scopeValidatorMock->expects($this->once())->method('validate')->willReturn(true);
+        $this->configWriterMock->expects($this->never())->method('save');
+        $this->configWriterMock->expects($this->once())->method('get')->willReturn('existing_value');
+
+        $processor = new ImportProcessor($this->configWriterMock, $this->scopeValidatorMock, $this->scopeConverterMock, []);
+        $processor->setOutput($this->outputMock);
+        $processor->setFinder($finderMock);
+        $processor->setReader($readerMock);
+        $processor->process();
+    }
 }
diff --git a/docs/config-import.md b/docs/config-import.md
index 4b4e8c4..bbe0bb1 100644
--- a/docs/config-import.md
+++ b/docs/config-import.md
@@ -123,6 +123,28 @@ vendorx/general/api_key:
 
 This is helpful when you've got the same settings across different environments but want to keep one environment ( `X` env) unchanged without showing the exact value in the config file. It's a common scenario, especially when dealing with sensitive data. You really should only keep that kind of info in the environment’s database, not in your GIT repo.
 
+### If-Not-Set Modifier
+
+To conditionally set a configuration value only if it has not been set previously, use the `if-not-set` or `if: not-set` modifier. This is useful for setting initial configuration values for third-party extensions.
+
+For example, this might be the content of your config file:
+
+```
+path/to/config:
+  if-not-set: true
+  default:
+    0: 1
+```
+
+Or
+
+```
+path/to/config:
+  if: not-set
+  default:
+    0: 1
+```
+
 ### Recursive folder setup
 
 If you choose to store your configuration files in subdirectories, e.g. per vendor, the recommended folder setup should look like this: