In the upper-left corner of each viewport is a label bar that consists of three labels. Each label is a clickable shortcut menu to control viewport display.

Viewport label menus
1. General menu
2. Point-Of-View (POV) menu
3. Shading menu
An additional viewport label menu appears when you enable 2D Pan Zoom mode.
Load Custom UI Scheme to load a different CUI file, then reload the original CUI file again. The label bar will become available after either the new or original UI scheme is loaded.