This is the source code of Vampire Survivors Save Manager.
This save manager gives you more ease of access and also creating clean saves for vampire survivors. And also brings the possibility of using the new game plus system to reset your save progress, while providing some benefits for your new playthrough.
The only thing it can't do, is update the checksum of the save file, so you'll need a tool that edits Vampire Survivors save file to update the checksum.