macOS Mojave offers a convenient — and fun — Picture in Picture (PiP) feature. You can “float” a video window from Safari or iTunes over your desktop or a full-screen app. It’s easy to implement on a MacBook Pro with Touch Bar. Here’s how:
Open Safari on your Mac.
Go to the website and video you want to play and start playing it.
Click the PiP button on the Touch Bar.
To adjust the PiP window, drag it at any of the four corners of the screen.
To disengage PiP click on the PiP icon on the Touch Bar or the PiP button in the window.