After having beat the single player campaign (and having a fabulous time doing so i might add) I am trying to find how to reset the campaign to "new" status.....i have uninstalled/reinstalled.....checked for save game files ect but i can not find what i need to find to reset it to "new"

Delete the file "shell.set" in the saves folder inside the game's installation folder.

ive tried this but as soon as it resyncs with gog it brings back the campign progress