With a left-click on the marked icon (1), the submenu items can be hidden. The result is an enlarged workspace, see below.

In order to show the submenu items temporarily, you will have to move with the mouse over the gray bar (1).

In shielded condition you can change the submenus of each main menu as well.

With left-click on the 'three lines' (2), the submenu can again be displayed permanently.