I'm using GNOME Flashback (No effects) on Ubuntu 13.04 and I've got six workspaces however when entering System Settings -> Keyboard -> Shortcuts -> Navigation I only see options to address the initial four.
It used to be options up to 12 workspaces there and as I certainly don't need that much, I want to have at least enough for the amount currently active.
How can I restore or add more shotcuts specifically to navigate and move windows to workspace 5 and 6?