After upgrading to Clarity 16.0, the expand / collapse option is missing at the top of the Modern User Experience (MUX / UX) left-hand navigation menu. This would allow you to display the menu names next to the menu icons. For example, next to the Project Tiles icon, you could see the Project Tiles name.
This is working as designed. There have been some improvements added in Clarity 16.0 to the left-hand menu in 16.0 including:
Clarity 16.0 and higher
You can hover over the icon to see what the name of the menu item / module is.