Keyboard Volume Controls Remapping?

HP qwerty keyboard has volume controls as follows:

F7 = mute
F8 = lower volume
F9 = increase volume

LibreELEC on a LePotato board, the keys behave as:

F8 = mute
F9 = lower volume
F10 = increase volume

How/where do I correct this mapping?

Also, is there a way to use a mouse (like the wheel of the mouse) for sound control? This way I do not need to keep a keyboard around all the time.

To remap keys I found keymap editor add-on.

For the mouse there is a wiki, but I can't work out how volume control would work for the click wheel when turning and clicking.

- turning = up-down scrolling
- click-turn = up-down volume

Possible?