Zone Doctor+ problem

Yeah, just this week I realized that ignoring the error message at saving does not cause later problems... so far I haven't tried editing the tilesets themselves, only the map tiles like normal.

Your comment is very timely though, I'd like to ask you about the possibility of using different combinations of tilesets in one same map. I might be mistaken but it looks like Zone Doctor gives you the option to switch a map's default layers (1, 2, 3) to the layers of a different tileset; like, say, opening the Zozo town map and switching its default "layer 2" to the layer 2 of Castle Figaro or something. Making odd combinations like that. I don't know if it's viable but it could lead to some interesting scenarios.

I quite like messing with map editing, I think I have a good eye for it.

About importing maps -- that's bad news for me, I have the habit of exporting/importing my edits, for backup purposes. Do you just backup the entire rom, then?