EDIT - I stand corrected from Keithcurtis, I didn't know about that feature (and we posted roughly the same time lol) If looking to have a base copy (or first copy), as Rick A said, I personally copy game before making any changes, rename the copied game to something else, and use the new copy, keeping the old for next time/group. Example: I have Lost Mines of Phandelver (MAIN) which is my main backup, and my Saturday group I copied it and renamed to Lost Mines of Phandelver (Sat) If you are looking to change an existing game to a previous version, or before you did any changes, sadly there is no way except redoing everything from scratch. (unless it is a paid module, in which case just remake the module)