The main menu page is accessible from the browser app header at all times and offers you all the available functionality at the present moment.  So it may look different to this depending on your permissions level and current selections.

The functions available from the menu have been grouped together into topics to help you find the item you require.  You can return to the navigation diagram at anytime by using the Show navigation arrow in the sidebar.

Note when in small browser/portrait mode the menus rearrange so all are showing vertically down the page.