@broekjwI cast Demiplane; enter the room; let the door expire. Do I have a way of getting back? And what if the door’s dispelled? The spell's description tells you: you're trapped, but you can cast the spell again to reopen the door.
— Jeremy Crawford (@JeremyECrawford) April 28, 2016
@broekjwThanks! Before I cast again, caster X visits my demiplane. Does my new door go to his original location or mine? You open a door to a new demiplane, to one you created before, or to one you're familiar with that was created by someone else.
— Jeremy Crawford (@JeremyECrawford) May 3, 2016