script.brightness

This is a kodi addon that will open the brightness dialog with the touch of a button.

Attach this addon to a button press in your keymap.... below is the letter F.

<keymap>
    <fullscreenvideo>
        <keyboard>
            <key id="61510">runaddon(script.brighness)</key>
        </keyboard>
    </fullscreenvideo>
</keymap>