Yes, I'm afraid there won't be any easy way to do this until a future update. You might be able to pull this off by playing some tricks with the Rank system, though. Reset all cards to rank 1, then set cards to advance to the next rank after 1 correct answer "in a row", then start a session with a limit of 50 cards; mark each of those cards correct. Then, go into Card Settings and set it to only review cards of rank 2 or above. Now you'll only get those 50 cards in each review session. You can go back and set the rank system to advance cards to the next rank after 3 in a row or whatever other threshhold you like, just make sure that you keep the "Retreat" checkbox in Rank Settings unchecked so that those 50 cards won't be returned to the larger pool. Once you've memorized that set of cards, go back to the 1-correct-in-a-row setting, configure Card Settings to only review cards of rank 1, start another session with 50 randomly selected cards, and mark each of those correct, then set Card Settings back to rank 2 or above and you'll have another set of cards to review.