Restart on mastery questions?

Hi all,
About two years ago, Khan Academy rolled out the "start over" link on quizzes. This was rolled out on just about everything except for course mastery quizzes, however, in the announcement, it was promised to be implemented in the near future. If not scrapped, I would like to request for that feature to be enabled on course mastery challenges, as it is quite frustrating to fat-finger a question, or not entirely be prepared to take the course mastery challenge, and be forced to slog through 30 questions, only to end up further back than before. It is almost like a punishment for challenging oneself, which I feel distracts from the site's mission.