How to remap a key that's not captured by xev?

I have a mechanical keyboard (by Duck) that includes a Fn key used with F10 to trigger Win-lock (disables Windows key so it doesn't bother when playing) and N-Key rollover.

As a programmer, I don't actually use any of those, but I would like to make that Fn useful as a Meta/Super key for some keystrokes (I'm a rightie, the mouse's on the left side) or alt-window movement.

However, when trying to get the key data running xev, it does not output anything - different from simply pressing Super, that tells me it's called Super_L. I can see it works, though, as by pressing Fn+F10 my Super stops working, and Fn+F12 outputs 10x something like this on xev after the key's LED stops blinking:

MappingNotify event, serial 39, synthetic NO, window 0x0,
    request MappingKeyboard, first_keycode 8, count 248

Is there anything that can be done so I can remap this useless but importantly-positioned Fn key to something really useful? D:

Solution 1:

Not a solution, but an answer to explain Fn (which have no standard implementation)

Fn× handled by BIOS/Firmware or driver.

Some vendors provide a way to customize them with limited options. If you are comparing with MS Windows, some vendors supplies tools with their binary drivers that can talk to BIOS some how.

If it's handled by driver, See How do Fn keys work? or precisely Linux And Samsung Series 9 Laptop Fn Keys. Dell laptops uses dell_wmi kernel module. Look for other driver in the same folder. Such case, it is possible to customize the kernel module.