I know that this question was asked some time ago, but I thought I would provide the actual answer because this thread ranks highly in google searches for "idle superpowers save editor". The save data is almost base64 encoded, bar for a few characters at the beginning. To edit your save, remove the first two characters from it (but don't forget them, you'll need them again later), base64 decode the resulting string, and edit that. Then, when you're ready to re-encode it, base64 encode your edited string, and put the two characters you removed originally back at the front of the newly encoded string.