I use a VirtualBox Windows 7 guest in seamless mode on an Ubuntu 12.04 linux host running Gnome 3.
Under normal operation when VirtualBox is not running, pressing the Windows Key on the keyboard launches the Gnome activity panel.
When the Windows guest is running and is in the foreground, pressing the Windows Key opens the Windows menu inside the guest.
Is there anyway to configure it so that the Windows Key will be ignored by the guest, and passed through to the host?
Yes. Open the VirtualBox Manager window, and go to "File" menu, "Preferences" (Ctrl-G).
Under "Input", uncheck the box labeled "Auto Capture Keyboard". There is no need to restart the VM if it's running, so this can be changed "on the fly".
ubuntu-20.04 as host and windows-10 as guest here.
I have similar problem but solve in a different way. I leave my guest fullscreen in a empty workspace and use hot-corners to switch between workspaces (guest and host)
This are my steps:
cat workspace.next
cat workspace.previous