Platinum Arts Sandbox - Free 3D Game Maker Forum

Oh well thats what I was told

Okay, you dont need to delete the my_stuff folder. You just leave that as is. What you should delete are the "config_*gamemode*.cfg", then enter game and select "Restore Defaults". Job done!

To add onto Leo's point, changing from co-op edit, to Single Player (or run around) mode, simply go to Menu>Load Map>Gamemode tab>Run around.