Not specifically to the KWS, unlike Chaff or Heatsinks there is no specific binding for it. All you can do is bind it to a firegroup and have the KWS in that. afaik. Haven't looked in bindings for ages.
From what I recall, the KWS is treated like a weapon and must be bound to a trigger of which there are only two available and you will have already assigned them in the bindings.