Hi Rome,
Expert mode has 3 options.
If you want to retain old values and merge new with it, there is the 3rd option. Now try to generate a profile with a new name and save it. Goto PFCG again and view the authorization profile.
I would suggest you to read a good thread on this.
difference between "change auth data " and "expert mode" in pfcg
Regards,
Divyanshu