Isolates the selected elements, so that other elements in the model are transparent.
- Navigation tab
Selection panel 
Isolate - Right-click menu
Isolate - Shortcut: Alt + I
- Select the elements and click
Isolate once to isolate them. - Click
Isolate again to reveal all elements in the 3D Model Viewer. NoteIn the Options menu, you can control the transparency of elements. Click Navigation tab

Tools panel

Options.