Every single lesson I save, no matter which playlist I save it to, always appears on my "Continue Studying" list, and removing them from the list also removes them from my playlists. I think it would be more comfortable if that list would only contain the few lessons I'm actively working on (for example, only add a lesson to it if I've opened it, regardless of whether I saved it or not, and make no changes to saved playlists when I remove it), and have my playlists be a completely independent entity that has nothing to do with continue studying.