How to Use Custom Function of 50S ii to set Shoot without lens On

[rollsman4]

I am using GF lenses and want to use Pentax 645 120 A Macro with adaptor. I dont want to go into the menu to change this setting when I switch to my GF lenses. Can I do this and can you explain how to do it. Thank you

[Greybeard]

Is there a reason to not just set this on and forget about it?

I rarely use third party lenses without an intelligent adapter but on my X series cameras I always have this setting on.

[rollsman4]

How can I set this up ?  Can I use one of the Custom Functions Buttons?  Thank you