Bookmarking Questions/Practice Problems

One feature that would be extremely helpful is the "bookmark". If there was a button to save certain questions or problems (as we are working on them) that we found difficult or noteworthy, it would be easy to refer back to those problems later. Perhaps they would be saved under "Bookmarked" or just "Saved". This way, all the individual problems would be accessible at a glance. 

(I know that the Timed Mini Sections have the bookmark feature, but it is only visible DURING the test. If this bookmark feature could be seen outside of the test, separate, and extended to practice problems, it would be much appreciated.)

Thank you!