You can! The feature is called Desktop Mirror. It's disabled by default since it doesn't work with all GPUs, but here's how you can enable it.

Once you've enabled it, you'll see a desktop mirror on page 2 of the Show Tools menu.

If you're into building custom sets in Unity, you can also embed it directly onto objects in your set using our ScreenElement component. One show used that to embed a desktop chat window into a crystal ball.