Displays or hides the red indicator representing the current workplane.

WorkPlane hidden

WorkPlane displayed

Note: If Workplane by Face mode is checked in the Drawing Aids window, the location of the workplane will change temporarily when you highlight a facet and create an object on it. As soon as the object on that facet workplane is finished, the workplane returns to the default location.

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.
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.