I had same issue on UX480. After Windows Update, Screenpad extended is black. Tried everything, Toolbar Update, Driver Update, Nvidia Update, Screenpad Driver Update. But nothing worked. Black screen with little mouse icon in the corner.
Solution: Go to Device Manager, Graphic Cards, select Intel UHD 620 and right click "Update Driver". For whatever reason, the driver version was 24 after Windows Update. Now after update, its 25 and screen works again.Before that, I went to Windows Update Center and selected the Asus HID update, maybe that is necessary too.