I think the custom flashcard feature needs a bit of work to make it really useful: I've been trying to use it to set up a few sets with My Vocab since those are the words that I've struggled with. I'd really like to set up sets of about 100 words to make them manageable.
Firstly an issue: I find that when I try to import, it only saves them sometimes, less than 50% of the time. Usually it says it saves it but the new ones are not actually added to the set. Sometimes it works.
But it would be helpful if:
1. There was an "add all" function. Adding hundreds of cards is really painful.
2. There was some way to "add new" cards. So if I set up a set with the first hundred, there is no way to know in a second set which of the cards are already in a set. Similarly, when I do a new lesson and add another 10 words, there's no way to know which ones are the new ones.
3. It would be great to shuffle the cards when going through them.
4. It would work better if you could hide the list while you're trying to add. Since I have to press "Add" on every single card individually, the list at the top keeps getting bigger and scrolling the import list down.
5. Anki-style remembering of which cards have been rated easy and which are hard, and therefore rating the harder ones higher for redisplay.