This may seem unrelated, but it’s part of the same process. For some reason when I imported the music as XML, Dorico/NP assigned a Horn “in B flat” to the Horn parts. I need to change the instrument to a Horn in F, not only for staff labeling purposes, but also so that the transposition is correct in the part. The sound won’t change much. However, when I click on Change Instrument, no window opens, nothing happens. All other options on the list, Edit Names, etc. work fine…
I have rebooted just in case, but no luck.
