The name of your character in hexadecimal is the name of your save file. It is not stored in the save file. You might try converting a new name to hex’ and editing file names, or making a new character with the name you want and then replacing all the contents of the new character’s save files with contents of the old character’s save files. Don’t know if either of these methods works.
EDIT FOR POSTERITY: the name is in base64, not hex, and must begin with the character #