I don't think it was a dream... I think in an early version I had drag-and-drop rooms, but I ended up needing to drop that (no pun intended) in a ui overhaul for being too complex to re-implement. You can move rooms around with a bit more trouble by exporting/importing them.
BUT: I've added a new secret button in the sprite extras menu! It will let you convert any sprite (well, as long as it's not used for multiple tiles across the world) into the avatar. (I was moved by your needing to edit the data in notepad++.)