Displays or hides the red indicator representing the current workplane.
WorkPlane hidden
WorkPlane displayed
...
Initially the indicator is sized to fit the entire window, but you can change this, as well as the angle and location of the workplane (see Editing the Workplane ).
You can also display the origin of the workplane coordinate system by opening the Preferences (Options / Preference) and checking Show User CS.
Fit to Window
...
Fits the workplane rectangle to the current window. This is useful after a view change such as zoom or pan.