I'd really like it if the site would simply save the difficulty level filter when browsing the library. Ideally, opening the library would return the user to place he or she was last (same difficulty, same page, same ordering). Right now, when browsing lessons, I have to open a separate tab each time I select a lesson, or else I'll have to re-input the difficulty filters every time. If I'm only interested in intermediate and advanced material, seeing the beginner lessons first shouldn't be the default. It's a very frustrating part of the interface, to be honest.