To expand the menus temporarily, hover over them to open the menus and select the tab you want to open. When you remove your mouse from the menu area, the menu will collapse again.
To keep the menus expanded, you will need to pin it. Click on the staggered bars icon at the top of the menu, this will ensure that the menu is kept open at all times.
The diagram content menu can also be expanded to cover the whole width of the page. To do this, simply click on the two arrows contained in a circle on the side of the menu to expand the menu as seen below.
Take note that when you do this, the left navigation menu will collapse automatically and has to be pinned again if preferred.