This SPanel (S for 'sliding,' 'secondary' or 'special') displays contents selected by buttons that look like this:

Try Me ☰

You have to actively click on the "hamberger" icon on the top left—either after or before clicking the select button—to view the contents. The displayed content will not be removed until you select another item to display. Remember to close this panel (click on the maroon tab with a 'times' icon on top right) to get back to the main contents.

It may be asked why does activating this panel require two actions: first, to select the content, and then to open the panel. It certainly is not because of any technical difficulty. This panel is reserved for contents that are useful but only in a secondary manner, as an aid to the main content you are reading. By making you take two steps, we deliberately remind you to concentrate on what is at hand and not be distracted, which is easy to do.