Using the shortcut toolbar is similar to using any of the given measurements themselves. If a measurement requires a selected part or surface (such as in a volume calculation) then the shortcut toolbar button is not active until that prerequisite is met.
To show the shortcut toolbar when loading files,
Go to the 3D Viewer settings or 2D Viewer setting (which ever applies).
Click on DEFINE SHORTCUT TOOLBAR...
Check Show On Load.
Click OK.
To toggle the shortcut toolbar on and off,
Press Ctrl-T.