I test out a method to revert the entire project to a last manually saved state, and various methods of undo with unstable results. For now, I decided the most stable method of undoing a large mistake you made is to include this revert button (for the next release).

RPG20XX loves to save all the time to make sure no data is lost, but this is a problem if you accidentally put a large mess on the current map. Every operation you do (change current map, close, etc.) will save the map with the mess. This button will fix all that now. You'll have to remember to save after every good change if you really get paranoid, though.