https://www.polygon.com/2018/5/4/17319866/steam-switch-pro-controller-support-how-to

Steam will support the Nintendo Switch Pro Controller beginning with a Steam Client Beta update that released on Wednesday.

The client makes the Pro Controller fully bindable and customizable, including such features as its gyroscope and vibration. Settings are changed through Controller Settings page, which is the same page that configures PlayStation 4 and Xbox One controller support.