Use a robust text editor like Notepad++ or Visual Studio Code . Standard Windows Notepad can sometimes corrupt file formatting.
The general process, as referenced in game communities, is to open your save file's content in the JSON editor. From there, you could theoretically locate and alter variables related to:
If you are looking to get a specific outcome, tell me which character's route you want to unlock or what item you need, and I can give you more specific instructions. Save Editor