I was thinking, since the rooms can be modified through .sav file, the character information should be able to be modified as well. So I tried it, and it worked.
First, find the character's name, then continue searching until you find "slave_class". Just like this.
and change it to
"slave_class":"slave1"
This works well when you have few characters and only need to modify one or two, but it can be cumbersome if you have many characters to modify. or you have a very complex character relationship, the name may appear in many places, and you need to find information that only corresponds to that one.