You can manually change your save data if you know what you're doing, but it's a pain in the ass. The save files are image data (the save thumbnail) concatenated with JSON data (the actual save data). The JSON stuff should be easy to change, but because the image is binary and the JSON is UTF-16LE, most text editors will shit the bed trying to properly read it. You can use a hex editor to copy the JSON data to a new file so text editors will play nicer (assuming they handle UTF-16), and then pass it back into the original file with the hex editor. And even then, you might need to understand the code itself to figure out the fields you need to change. Honestly it's easier to just patch the game to adjust whatever you need to than to directly mess with the save file.