Hello, PavelE,
Thank you for your suggestion. However, I am running Catalina and not Tahoe on my mac. I'm not sure what you mean by System Settings. There is System Preferences but I am not finding Menu Bar or any option for Allow in the Menu Bar under System Preferences - no "Allow in the Menu Bar" list.
Parallel Toolbox will open when I click the icon on the dock. It will appear on the menu bar and then close as if it times out. This occurs in well less than a minute.
I'm afraid I am also not finding the "Show in menu bar" option in Parallels Toolbox settings which I assume would be under Toolbox preferences - I find nothing actually listed as "settings'.