How to Disable Desktop Previews for Taskbar Live Thumbnails in Windows 10
In Windows 10, when you hover over a taskbar button of a running app or group of apps, a thumbnail preview appears on the screen. For a single window it shows a single thumbnail, and for multiple windows it shows a number of thumbnail previews in a row. When you hover over a preview thumbnail, it dims other open windows and shows a preview of its app. If you want, you can disable this feature.