How can I access the window menu for a VirtualBox VM in XFCE
Pressing the host key (Right Ctrl by default I think) will change the context of where the keyboard keystrokes are being sent and also allow you to open the Host XFCE window menu for the Guest VM. Just press Right Ctrl once and you should see the VirtualBox down arrow icon in the bottom right of the window change color and then click on the XFCE window menu.