The ability to shift all tiles within a tile map by X and/or Y.
I have had to recreate maps before by making a mistake on dimensions, and often I find completely remaking the map is easier than trying to shift by hand by copying my work over, but still extremely tedious.
Also, if possible, toggling collisions on individual tiles! I have hacked it in before by simple deleting the number of collision points in the polygon until I have three and then placing those on one point (such as the top left), but having an official toggle would be so much help.