@daviek not been using zwift all that long so you’ll probably get a better answer, but no one’s bitten yet!
From my limited experience :
If you sign up to an actual training programme then you are given X number of workouts per week, it seems you can pick which order you do them in within the week, but once the week ticks over, you get the next lotmof workouts.
If you just flick through the individual workout menu instead, there are training programmes you can follow where you just pick the next workout from the list each time you go on.
When You’re actually doing a workout, you can swipe away each segment you’re on, skipping to the next one, thereby shortening the workout.
Can’t say how this stacks up against trainer road, not had long term experience of that either!!