Thank you for great update. Expression maps are basically a good idea but at the moment they provide not so many options when compared with advanced VST Instruments. For example slurs are not playing back with Vienna Instruments. I wish there were a second layer in play mode (which could possibly be played back but not connected to score) and then a pen to edit key switches in that second layer. Of course, it would be nice to have possibility to do some basic control changes in that layer also. As Cubase is outstanding DAW for VST like Vienna Instruments I believe this kind of solution might be not so difficult to accomplish. This layer then could be combined with score data when exporting music to DAW for further editing. This kind of solution could give users also another way to change expressions. Ideally notation software should offer such possibilities for playback that not every work should be imported to DAW which is the case nowdays.
It is our intention that Dorico will have some support for controllers in Play mode in a future update.