Hey! Navigate to "C:\Users\[your_username]\AppData\LocalLow\Orsoniks\CasualtiesUnknown", and you should be able to create a backup of "save.sv" in another folder, or just rename it to "save1.sv"
(if you can't find your appdata folder, Press Win+R and type "%appdata%", Enter, and then go back a folder.)
Have fun!