Can I set a gnome keyboard shortcut to be a prefix key, like in emacs, tmux or screen?

I would like to setup some Gnome keyboard shortcuts to be a prefix-key, so that I can add several shortcuts with the same prefix. Eg. I'd like to be able to have Super+x be a prefix key, with the next letter determining the application to launch: - Super+x f starts firefox - Super+x e starts emacs - Super+x t starts gnome-terminal Etc. Also, something like k as a prefix to workspace manipulation commands: - Super+k Left workspace left - Super+k 4 go to workspace 4 and so on. This is a natural analog to what emacs, tmux and other applications do with configurable shortcuts, and I can do this with the stumpwm window manager as well, but I wanted to try Unity on my new laptop and was trying to get the same efficient setup I had with stumpwm. Is this provided for in Gnome? Do I have to do some trickery to do this? It would be best if I could find a way to do this in gnome's keyboard shortcut editor.