Just create an XML file in
/usr/share/gnome-control-center/keybindings/
with the keys. Done.Here's an example of a little mapping I did for Compiz's Scale and Expo plugin.
<?xml version="1.0" encoding="UTF-8"?>
<KeyListEntries wm_name="compiz" package="compiz" name="Extra">
<KeyListEntry
name="/apps/compiz/plugins/scale/allscreens/options/initiate_key"/>
<KeyListEntry
name="/apps/compiz/plugins/expo/allscreens/options/expo_key"/>
</KeyListEntries>
The result?