You already have two ways to study your whole collection:
-
Create a parent deck and make all your other decks children of it.
Advantages: Works just like any other deck, inactive decks can be simply removed per drag and drop.
Possible disadvantage: New cards will be fetched from the child decks successively (not randomly from the whole collection). -
Create a filtered deck for the whole collection (requires the new scheduler).
Advantages: More options, complete randomisation is possible.
Disadvantage: More complicated to set up and use.