I also posted the following on the VI-Control forum:
I’ve got a 2nd monitor on my iMac connected to the display port. When I drag the NotePerformer mixer to the 2nd monitor there is a resolution change so the mixer is magnified and only part of it can be seen e.g. the pan and channel titles are gone as well as the title bar with global volume and reverb. Also only 8 channels out of 16 can be seen.
The mixer window also loses focus so it is not possible to adjust volumes. Looks like the mixer only functions within the scope of the Dorico app.