A preview mode to test scene changes and make adjustments without actually effecting anything live.
already requested and discussed many times
would still be a good idea… 
It’s probably hard to implement. Having that functionality on Director (while bein online with the system I mean) might be easier to do.
Preview is present in most other flagship desks.
I use it regularly on Yamaha QL and CL desks, as well as Avid Venue.
It shouldn’t be hard to implement.
Will A&H comment if this will be implemented in future?
This is a useful and needed way to work, its a must while in a rehearsal setting at a theatre. Or while in a show, and you need to make adjustments to following ques later in the show on the fly, while playing a different song! A really needed feature!