Thank you, appleianer! Mostly understood. I just have the problem, that on the line "The hot key _____ is pressed", KM seems to expect a KEY (!) to be pressed. Just "click" seems not to work; in other words, the line cannot be activated (not possible to have the white "v" in blue at the beginning of the line) without defining a KEY.
Which leaves me with still having to press at least one key, instead of just a mouse click (any type of mouse click, except 'left mouse click', would do (I am working with a mouse, not trackpad).
What am I missing?