I think it would be really great if you could have a list in your own personal drawspace telling you all of the lessons you have viewed previously and which allowed you to go back and look at them so you could continue to change or work on something.
I don't know about anyone else, but I sometimes I don't quite finish a lesson before I get to view a new one and do so. I'd love to be able to go back and keep working on the ones I've already seen.
Kara