Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding Troubleshooting ScriptItem has changes but is not writeable ...

I don't know if it's of any help, but I had this (or a similar) issue in D:OS 1 and just had to remove the pak file from the documents mod folder to make story goals writable again.