I am looking to notate something similar to this screenshot (Corigliano 1, 1st Movement). The trumpets and horns go from five lines and three lines, respectively, to a single line for both instruments. Is there a way to do this in Dorico?
Welcome to the forum, @Benfullerva. Yes, Dorico can automatically condense music belonging to multiple players down to a smaller number of staves. Perhaps take a look at this video to start to get a sense of how condensing works:
Here are a couple of further videos: