I am not sure if this has anything to do with Dorico, but I wanted to mention it anyway.
I am working with 2 monitors and have Dorico open on one display and use the other display often to see the Layout Options dialogue, Notation Options dialogue and Engraving Options dialogue at the same time.
Same with menus from the Dialogue windows: When I open a popup menu, that popup menu is showing on the second monitor, not in the Dorico display.
Also, when I hover over items to see tooltips, these tooltips show up in the second monitor, not in the one that displays Dorico.
It’s fun, but probably not intended behaviour.