the perspective view settings are saved when you save the view. change the perspective mm to whatever, then save the view. then change the perspective mm to something else, and save the view. you can switch between them with that.
The procedure is slightly different in the latest Creo 184.108.40.206 as they have combined the view orientation dialog and the perspective view dialog into a single dialog.
hope this helps. if it does, please be sure to mark as solved.