2 gang switch query?

i have a 2 gang switch on the wall (it has 2 switches) one of them switches on the garage and box room light at the same time. the other switch does nothing.
i switched off the power and opened the box, and discovered the following.
the switch that does the garage and box room light is wired as
Red - comm
Blue - L1
yellow - L2
earth to back box earth point.
the switch that does nothing has no wires connected.
with the configuration of the wired switch as it is, is it correct?

is it possible to utilise the second switch by wiring it up using twin earth cable some how to power a different light (i know i need to jump across com to com) but what else??