A recent post in the Zonbu support forms brought to light the extensive keyboard shortcuts available to us as Zonbu users:
Most of the shortcuts are either Windows or XFCE shortcuts. If neither of these work, the shortcut probably does not exist. Here, the XFCE default shortcut Ctrl-Alt-D does what you want.
The offical list is here: http://www.xfce.org/documentation/4.2/manuals/xfwm4#keyboard_shortcuts but we have several customizations.
You can review and edit system keyboard shortcuts in Control Panel > Advanced > Keyboard > Shortcuts — assuming you know how you would create the effect of the shortcut in command line… which is why it’s hidden in the advanced control panels…
I wanted to pass it along for anyone who missed it.