Is ProMdlErasePreAction helps. I could see no close event. or you can use save the event.
There is not point in getting a close event when the model is closed. that's why PTC might not expose this event.
I understand currently there is no such event available. I am interested in a particular case when the user closes the CAD while model is still open.
user_terminate should help. As far I remember no event is fired, but if you want to distinguish between unload und exit you must prepare your xxxtk.dat.
I would assume that this functions will not allow to overwrite PTCs ones