After some exploring, I resolved my own question.
When clicking on the Key of the Song icon, I get two columns listing all keys. In the right column it says (No Transpose) and if I change this to C (or Cm if the original is in a minor key) It will have the desired effect of writing out the music in the key of C, which has no accidentals, but the pitch and note or chord values remain the same.


I used BIAB quite a bit in 2008 and after a 16 year break(!) I'm back with version Mac 2024.