Hi there :) First of all I'm not sure if I got right your question... But I'll try to help you out anyway ^^
So, after you've completed a workout on this app it shows you a window... At that point you can tap "too easy", "right on" or "too hard" in order to let the system now if the difficulty level is the one that suits you, I think. This way you'll be probably suggested to try other workouts, easier or harder ones and so on. In that same "window" you could also take a note below. Tap to type there. It will show as a kind of comment along with the workout on your profile... But it would also be visible when you'll check your "history" of completed workouts.

It's good to document ur progress