Dragging an non gojs object onto a diagram

As far as i understand the ExternalObjectsDropped event handler is dealing with native GOJS parts that where dropped.
Is it possible to drag and drop an external object onto a diagram which is NOT a native gojs part ?

Yes, but you need to implement it yourself. For example: HTML Drag and Drop, and external Clipboard pasting.

Or if you are old-fashioned: HTML Drag and Drop