Just testing out practice mode, I found what I really wanted was to be able to stay at a certain level until I felt I was getting good at sequences of that length, not immediately get pushed to the next level every time even when it took me 8 tries to get the 4-note sequence right. Give me a chance to feel like I'm improving! Don't just keep giving me harder things when I keep struggling with the existing ones.

It already has that feature! :) It’s just not very obvious. If you click the small lock icon near the top, it will snap and to that difficulty so you can practice only sequences with that specific number of notes.