How to transpose a minor second?

[judddanby]

This other very recent thread might offer additional insight:

Semitone Transposition

Hello All I know this is answered elsewhere here, but the solutions given didn’t work for me. So I’ll try again: I’ve got a piece in B major that I’m trying to transpose down to B flat. The key signature is there (as in Dorico knows it’s in B), but the Transpose window does not give me the options of selecting a “minor second down” nor a “diminished unison” down (as I’ve seen in other posts). I can get it down to A (major second), but not B Flat. Very curious what I’m missing here. I’ve attach…