Oh but there's lots of editor's already existing.
GIMP.
Photoshop.
My personal favorite, Campaign Cartographer.
OK yes, a bit of snark there, but this is a repeating pattern I'm seeing, thinking the GM Mode is a one-stop-shop. Treat the GM Mode like the Dungeon Master's Guide and Monster Manual from D&D. Can you do a game with just those two things? No, not really. You need to do some work, maybe bring in some outside resources, before you can run your game. The GM Mode is much the same. You *will* have to do additional work and bring in outside resources, even if it's just Engine exports, to accomplish what you want.
