I have a piano score in Bmaj…transposing to the trumpet, I get D#m7 G#7 etc chords - not very handy though.
Sibelius has a very handy ‘prefer flats before sharps’ or visa versa function for transposition.
Is there sth similar in Dorico or do I have to respell all my chords manually?
Not that I know… But if you set your score in Cbmaj, then you should get the trumpet part you want !
Thanx, but then my chords in the piano part look weird…not such a great work-around, no 
Ok…this is a real problem.
My general-score is in E-majeur.
Dorico makes the trumpet score F#-majeur. Sorry, but like sax players prefer playing in keys with sharps, trumpet players prefer keys with flats.
If I change my conductor track to Fb-majeur, my trumpet part is in Gb-majeur. so far so good, but my notes within the score are all written in F#-majeur, so I get a sharp in front of nearly every note, but the general key is Gb-majeur with 6 flats…???..
Workaround:
Make an extra file, make the trumpet a ‘none-transposing -instrument’. Go to the trumpet part, go to the ‘transposition panel’ …‘choose interval → E-Gb’…that works. But of course that’s an extra file just for the trumpet part - I can’t use all the other instruments in that file.