written for trumpet c, need to transpose for trumpet b flat

Hello! I believe https://musescore.org/en/forum/11 is the appropriate forum for such a question. Here we discuss the translation of MuseScore Studio.

Nothing special.
Select a trumpet in C, E or F in the score and copy the notes 1:1.
Then select the staff/part properties and apply a new trumpet in Bb to that staff.
The pitch remains the same, but the notes are on different levels.