How do I mimic dragging and dropping a FBX to the hierarchy window with an editor script? C#

If I’m understanding the question correctly, you want to use this :

Instantiate an Object

Well emorobot is not entirely right :wink: Instantiate will clone the object, but it’s no longer connected to the orginal prefab. Of course since the clone use the same assets, like a mesh for example, those assets will be updated since they are just references.

To truly Instantiate a prefab you have to use PrefabUtility.InstantiatePrefab.

Keep in mind that this function is an editor function, so don’t use it in a runtime script. Prefabs are an editor-only feature at the moment. At runtime prefabs are just normal objects which can be cloned / Instantiated. The only difference is that prefab-objects are not in the scene yet.