There is a file called 'accel.cfg' located at root\browser\defaults\settings. It has the default accel key definations including ones for LButton.
You are allowed to add to KM your own special keys for LButton. That is done by opening the file found by using EDIT > CONFIGURATION > ACCELERATORS.
Just as a test I added the following line to my accelerators.
ALT SHIFT LButton = navReload
Now if I hold down the ALT and SHIFT keys when I click with the left button, my page is reloaded. Note that you must restart KM after making any change to accelerators. Just find an unused key combination and add your change.