This editor DOES work for the Steam version, I just tested it by giving myself some items and editing my magic list.
In order to avoid your save being deleted, goto the Load game screen in the game(Don't load your save)
Then run the editor and load your save into it.
This helps bypass the checksum crap that may cause your save to be deleted.
Also, backup your saves first just incase!
After you make your changes in the editor and hit save then load your game.
[Edited by DigitalIP, 12/7/2013 8:11:04 AM]
This is how it was done for the FFVII re-release too.