I've recently reset my collection and finished adding all of the cards i own that aren't already in decks.

The next thing I want to do is add the cards that are in decks, while adding those decklists. Is there an efficient way to do this without adding each card to inventory one by one, and then making a deck and adding the correct version of each of those cards to the decklist?

In a deck -> "Add Cards", there is an option to "Add to deck & inventory", that will auto-add them in both places at once.

Ah, thanks. I see now. I was using the little quick-add box and not the full one so I hadn't seen that.