Panasonic Toughbook CF-31AAA7J1M Reference Manual page 53

External Display
53
The pop-up icon displayed by Fn key combination appears only on the primary device.
<Only for model with touchscreen>
Set the internal LCD to the primary device when using the touchscreen. The cursor will move on the primary device
when you touch the internal LCD.
®
<When the Intel GPU is activated and the extended desktop function is used>
You cannot switch the display by pressing Fn + F3.