‘Sidecar’ for Secondary Displays
macOS 10.15 will also reportedly introduce a new feature called ‘Sidecar’ that will allow you to use your iPad as a secondary display for your Mac, as well as quickly and easily sending any app over to an external display without having to deal with dragging windows around.
The feature will apparently be part of an expanded window management system that will also provide shortcuts for not only moving windows quickly between displays — whether that’s a directly-connected external monitor or an iPad — but also changing full-screen viewing modes, tiling windows on a single screen, and more.