We are so happy with FD that we use it. A lot! As a result, we have a lot of decks of cards, and it would be so helpful if we could put the cards in folders and/or sort them in different ways.
I have to admit that I know nothing about making apps, so I do not know how difficult that would be, but it certainly would be helpful
Or possibly the ability to merge decks, so instead of having a separate deck for each lesson (which is what happens when you download decks), you could merge them together, and that would also work well with the whole automatic repetition part (which I am still working on understanding).
To reorder decks, tap Edit the use the reorder bars along the right (touch, hold, drag up/down). To create a folder, tap +, then "New Folder". To study multiple decks together at the same time, tap +, then "Combination Deck".