I have written code to randomize decks when they're created to support newly purchased decks. The 'split' command should still work, letting you split out exactly the cards you select. Let me know if its not and its making a randomized new deck by mistake.
Oh, and all your decks have been randomized. Consider they came that way.
All testers have been given an 'attax booster pack'. These are technically just decks of cards with just fewer to start and they can't accept merges. Probably possible for some odd messages where you draw cards from them into a hand and collect them back into it. Feels weird to restrict you to just merging them into the 'main' decks though since this is just freeform cards. Show me how dumb it is right now.