When the Queue toggle turned on, the Master Play button won't start processing all of the Compositions immediately, but will start them in a row - so when the 1st Composition reached its end, the 2nd Composition will start too, and so on - you can use this feature together with the Solo mode.
Composition 1 → Composition 2 → .... → Composition n
The Queue mode also has a Loop function now, so when the last composition reached its end, the Queue restarts from the first composition.
There is also a preference which can be set to start the Queue from the current Composition.