Virtual Tablet On/Off is a setting that can be assigned to a button on your pens, Quick Keys, or display. It is similar to the Switch Display setting in that it also invokes the Virtual Tablet feature. However, it does so in a different way.
For reference, Switch Display is, by default, assigned to the right Device Control button on your display. When you press a button assigned to Switch Display, it will bring up the Virtual Tablet, allowing you to control another display on your system; and when you press that button again, it will cycle to the next display on your system. Subsequent button presses will cycle you through each of your displays to the ‘All Displays’ mode and then off.
In contrast, if you assign Virtual Tablet On/Off to a button, it simply allows you to turn the Virtual Tablet feature on and off.
When you press a button assigned to this setting, it will bring up the Virtual Tablet, and when you press that button again, it will exit the Virtual Tablet. A key thing to note is that when it brings up the Virtual Tablet, it will bring you to the same Virtual Tablet view you used last. This can be a great way to quickly go back to a single display you frequently use without having to cycle through all of your displays as you would with Switch Display.
To assign the Virtual Tablet On/Off to the top button of your 3-Button pen.
Open the Settings panel, select the 3-Button pen, and select the button you want to use.
 In this case, I'm using the top pen button.
 Select Tablet/Display.
 Select Virtual Tablet On/Off.
 Your 3-Button pen dialog box will now look like the image on the right.
The top button will have the Virtual Tablet On/Off function assigned to it.
When you press the top button, it will open the Virtual Tablet feature.
When you press it again, it will toggle it off.
The Virtual Tablet On/Off feature can be assigned to any button on your Quick Keys, Pens, or Display.