Go to the navigation window (see image below).

Make sure that the navigation folder you wish to open is visible in the navigation tree by working your way down the navigation tree structure (see image below).

Place your cursor on the navigation folder you wish to open (see the first image below). When you place your cursor on a navigation folder you will get access to an icon called "Open" (see the second image below).

Click "Open" (see the first image below). When you do so, the navigation folder you are working with will open. When a navigation folder opens, so does its navigation card (see the second image below). Via the navigation card you can manage a navigation folder. For more information on how to do so, see section 5.6.5.