Hi Delage,

Thanks for sharing your feedback!

Unfortunately, Khan Academy has already decided not to implement a course reset feature, in order to prevent accidental progress loss.

If you'd like to restart a course, the best option is to create a new account (or a child account) and re-do the course using that account. It's also worth noting that you can re-do the content in a course an unlimited number of times, so you can effectively re-do a course using your existing account, you just won't be able to mark the completed content as incomplete.

Thanks for posting!