While it is nice that I can rearrange tiles, it is very hard to keep tiles organized, especially if I have a lot. If I'm making more complicated characters or backgrounds, it becomes very hard to tell them apart quickly in the editor.
Allowing some kind of folders would let me put all the tiles used for one element in a single, easily organized place.
I would love to have this too. I started yesterday and am already facing this problem. It is very hard to keep your tiles organized when your game grows larger and larger. This would absolutely solve the issue.