The latest Dev Channel build 25174 has some missing icons, which suggests that the Redmond giant might be in the process of redoing and redesigning the Shut Down icons on Windows 11.
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A new Windows 11 redesign tool called Rectify 11 claims to change some of the aesthetics of Microsoft Management Console, Administrative Tools and comes with the latest StartIsBack integrated.
The classic right-click Context menu that was present on Windows 10 can be enabled on Windows 11 by editing the registry. For those who don't want to do that, a tool has been released by Sordum.