Hello, Very simple, Editor/Inspectors do not get a OnSceneGUI callback within a PrefabStage/Scene as far as I know. And I very much need this callback ^^' Am I missing something ? Thank =)
It should get the OnSceneGUI callback fine in Prefab Mode. For example, for the Camera component, the Camera Preview overlay as well as the camera frustum handles are implemented in OnSceneGUI, and that works fine in Prefab Mode (at least here). If you're seeing something different, please file a bug report with repro project and repro steps. Thanks!