How can I execute code in the editor?

Is there a way to execute code in the editor without adding a script with [ExecuteInEditor] to the scene?

I don’t want to make a custom editor or property panel.

So you do not want a script in the scene, and you do not want a custom editor panel/window. You basically just want some code to run in the background or run when you press a button?

There are some ways to do that.

To have a piece of code always running and checking for something you can use the InitializeOnLoad attribute and attach a function to the editor update event as described in the documentation.

The other way would be to make a static script with a static function and attach a menu option to that function.

Example:

public static CustomUtility
{
   [MenuItem("MyCustomMenu/DoSomething")]
   private static void DoSomething()
   {
       
   }
}

There will now be a new menu item at the top of the editor where you can select and run the DoSomething function.