One can still try putting the trumpets in separate players from the flugelhorns and then combining each trumpet player into its own layout with the corresponding flugelhorn player. With the judicious management of system breaks and hidden staves, one can make each look like a single player on the part, and the trumpets and flugelhorns will condense when necessary.
I am sure that future plans are already in place to eliminate this exception, but the Team didn’t want to delay implementation of stage one until everything was possible.
Many aspects of Dorico have been planned for incremental improvement so that more areas of concerned can be addressed in some fashion for folks with different needs. The Team has come a long way and introduced some impressive capabilities into the program, so I look forward to what the future holds.
I fear, Derrek’s solution indeed is the most practical way to go currently.
Of course an instrument change should not stop condensing, but that’s how things are at the moment. There is no “make all instruments condense” switch.
Hot take: I don’t know how important playback is to you, but for the Trumpet/Flugel you could also add instrument change labels using staff text without actually changing the instrument. It’s obviously not ideal because that won’t affect staff labels (so in the full score you might want to repeat the Flugelhorn indication on every page) or playback, but it would at least circumvent the condensing issues.