Meanwhile, you could type kW*h into the unit field. It is then displayed as kW·h. I use it all the time in the integral field since it is more useful than the default kW·s.
However, if Mango considers kW/h to be an alias for kWh, that should definitely be corrected, as it could cause undetected incorrect numerical conversion issues. In fact, just today I was thinking of writing a function that used kW/s, so the possibility that someone may use kW/h is not out of the question.