I have an old Mazak ST-15 with FANUC 6T and the chuck ID/OD switch is located (hidden) in the rear electronics panel. Not very handy. That's all I can tell you.
You would think that with the evolution, Fanuc woud have made it easily accessible thru operator accessible parameter. I know Haas did. But then again, Haas is very user friendly. Can't say that for Fanuc.