Multi-monitor Task Switcher
As well as for the Taskbar, when working in a multiple display environment Windows® shows the Task Switcher (special service window displayed each time you press <Alt+Tab>) on the primary display only.
The Multi-monitor Task Switcher extension clones the original Windows® Task Switcher window on each secondary display so that you don't need to distract from your current attention focus:
Multi-monitor Task Switcher