This default shortcut may seem odd, given how frequently the pie is used.
But if you can access
Page Down using your mouse, it makes a lot of sense.
The Views Pie is one easily one of the most used menus in MACHIN3tools.
Primarily it facilitates quick switching between views in world space, and simplifies working with cameras
With the Custom Views option, it also allows switching between views in local and cursor space.
Beyond that, it supports changing navigation prefrences with the Orbit Selection button and Turntable/Trackball toggle.
The Smart Cam tool is used to create cameras from the current view, or to set the view to either the active scene camera, or any selected camera.
Check out the tool tips for details.
With mutliple cameras present in the scene, and the view set to one of them, you can quickly jump from one camera to the next using the Previous Cam and Next Cam tools.