Khan Academy is always looking for new ways to improve our site! The best way to get your feature idea visibility is to go to the Support Community section of our Help Center. You can find a link to the Help Center at the bottom of your dashboard, under Contact. Here's the direct link to the feature request forum.
You must login to submit feedback on the Help Center. Please note that the password is not the same as for your normal Khan Academy account. If you have not signed up for the Help Center before, there's a link on the login page. From there, you can see if someone else has already suggested your idea and, if so, you can add your votes to it and comment. If no one else has suggested it, you can be the first and others will be able to vote up your idea!
Thanks for your interest in improving Khan Academy!