KP_Insert is the 0 key on the number pad. Since you mention an Fn key, I'm guessing you either have a slim keyboard or a laptop of some sort. That means wouldn't have a number pad or its 0 key. At least not without it being enabled through, well, the Fn key or something like that, if some keys do double duty.
Curiously, upon checking my own system, the Insert keycode seems to be 110 not 118, but this might vary from keyboard to keyboard and system to system. Might be worth double-checking your own system anyway.
118 is associated with KP_MinPlus for me, whatever that is. Pretty sure whatever keypad key that is, I don't have one. (It's not KP_Plus or KP_Minus, which are what you probably think they are. There's also a KP_Comma entry, and I definitely don't have a comma on my keypad. Perhaps some other keyboards do, what with it being the decimal separator in some countries.)