The big icon with the streak and it turning red toward the end of the day really helps. Recognizing that some days you won't want to learn but just getting through it is ok. It's a really slow process if you're not deliberate but slow is better than none IMO.
A great experiment to do would be to sit people down and have a quiz application like Duolingo randomly choose answers, them seeing if the answers are right/wrong.
I suspect, much like experiments showing how people prefer/like (Familiarity effect) art they have seen in a previous session (even if months later and they don't remember and can't explain why they like it more than other art!), that students would pick up some correct/incorrect answers, because they can't help but read and notice any interesting differences from their mental model.
I have built an app which prepares exercises for you based on your subject and uses LLM-chosen emojis to represent each exericse. It notifies you with the emoji for each lesson each day with the idea of a visual cue but now you mention it using a dynamic icon for the app might be more important of a visual cue (to get the daily cadence/habit), rather than something recognisable