The Schema Design | Display Diagram command switches to the Content Model View of the selected global component—if the selected component has a content model. Global components that have a content model (complex types, elements, and element groups) are indicated with the icon to its left. The Display Diagram command is a toggle with the Display All Globals command. The currently selected toggle is indicated with a check mark to its left (screenshot below).
Alternatively, you could use the following methods to switch to Content Model View:
•Click the icon next to the component, the content model of which you want to display.
•Double-click a component name in the Component Navigator Entry Helper (at top right).