I wasn't clear enough, my fault, sorry. Usergroup change isnt' a must have. I used the user group in my old VB to then create an additional title e.g. "Gold Sponsor" - to be displayed beside/underneath the AVATAR. See attached screenshot
Now I am looking for something who can do similar in my XF2.
And b.t.w it really sucks that I have to ask you folks about your products , sometimes really simple stuff. Is there any source of help, e.g. manuals , beyond searching the forums ?