When selected a viewport, it appears with toolbars in the top right corner and in the bottom left corner under the mouse.
Top right corner - Display Mode:
Display Mode Wireframe
Display Mode Shaded
Display Mode Rendered
Display Mode Rendered Shadow
Display Mode Ghosted
Display Mode Technical
Display Mode Pen
Display Mode STL Repair
Display Mode Neon
Tripod
Pressing SHIFT key:
Hide objects
Show objects
Show Selected objects
Invert selection and hide objects
Swap hidden and visible objects
Lock objects
Unlock objects
Unlock selected objects
Invert selection and lock objects
Bottom left corner - Zoom:
Zoom Extents
Zoom Window
Zoom 1:1
Undo Zoom
Zoom Selected
Place Target
Rotate View
Zoom In-Out
Zoom Pan
Viewport Selection Cube