I discovered an issue where the macOS Mission Control functionality is altered. Normally when the Mission Control feature is executed (F3, or Magic Mouse two finger double tap, or the application) the active application windows in the current Desktop are reduced in size and the available Desktops are listed across the top of the screen (Screenshot Mission Control View.png). The user can then move application windows to other Desktops or navigate to another Desktop. When the issue is in effect and the Mission Control feature is executed, the active application windows in the active Desktop reduce in size and disappear completely and only the available Desktops are present at the top of the screen and there is no ability to move active applications to other Desktops (Screenshot Mission Control Issue View.png). Originally discovered in macOS 10.15 (Catalina) and continued after the upgrade to macOS 11.0 (Big Sur). An Apple Support issue was created (101190846755) in September 2020 and elevated to Senior Level support with their Engineering Department aggressively working the issue. I did not discover the root cause until 11/16/2020 that the issue is only evident when my Parallels Windows 10 VM is running and the instance I begin the shutdown of the Windows 10 VM the issue is immediately corrected. I then opened Parallels Support Case #2832452 and providing all the details related to the issue. Initial suggestions were make changes to Parallels configuration settings (Screenshot Parallels Windows 10 VM Configuration.png), which did not resolve the issue. This issue is not seen on my MacBook Pro which is intended to be configured the same as my iMac and I have not been able to identify any differences in their configurations or settings as yet. As Apple and Parallels continue to work the issue, I thought that their may be a Windows 10 configuration setting that is causing Windows to override the macOs Mission Control functionality but my research to date has not identified anything so I thought I would put it to the Parallels Forum. Appreciate any suggestions anyone may have.
