Custom key signature - vertical symbol placement for transposing instruments

The instruments in the flow are B♭ trumpets. I’d like to move the F# in their key signature from the top line to the bottom space. The Concert key current has an E natural on the bottom line, but that did not force the F# down for the trumpets.
phrigian

In the Custom Key Sig editor, use the octave down button
keysig

I have done that for the instruments in C. But it doesn’t get reflected on the B♭ instruments.

key

I don’t know of any way to customize the transposed sigs. I can’t find any mechanism for that.

Hmmm. And weirdly when I apply this customised sig to a transposing score I end up with a single G# for the Bb instrument!
keysig2

Surely this can’t be right?

Actually, check it out – as a B♭ transposition of that key sig, it is right. Minor with a raised 7th.

Surely it should be a single F#?

No, F♯ for B♭ trumpet would map to E♮ for a C instrument …

The Violin shows G minor with the 7th raised; that’s A minor for the Trumpet, with its 7th raised.

OK My brain fade!