This was mentioned back in the SM 15 days and supposed to be fixed in SM 16. When I hide the folders which is my preferred view it should be remembered if the folder pane is hidden or visible. I go to SM web UI and click the hamburger menu to hide the folder pane, navigate to another web site, return to SM web UI and the folder pane is visible again.

 

Please persist the visible state of the far left folder pane.