Change Taskbar Thumbnail Threshold to Show List 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 the number of open windows reaches the threshold, the taskbar shows open windows as a list instead of thumbnails. Here's how to change the threshold in order to reduce or increase the number of thumbnails to change them to a list.