Alright, I thought about it a bit more, and this is what I’m going to do:
I will add a “teleport” screenplay action on the hero, so you can teleport the hero to another location (in another level possibly).
This will open up a whole bunch of functionality, including what you try to achieve (turn a well into a portal).
So practically you will need to drop the door, and just keep the invisible actor. Then extend its screenplay with the “hero teleports to level … at position …”.