As a follow-up to my last post, I've decided to also configure my mk850 combo (k850 + m720 triathlon).

Some notes:

• The keyboard is usually connected to this PC through bluetooth. Since this is a change I usually do in the system for every keyboard, I added a rule for any bus (usb, bluetooth, etc)
• The mouse has an additional button that registers as a keyboard. Every press maps to three key events. I've disabled two of them and mapped the action to F19, in case I want to use it in my DE/WM.

evdev:input:*                                                        
 KEYBOARD_KEY_70039=leftctrl  # bind capslock to w 

evdev:input:b0005v046DpB015*
 KEYBOARD_KEY_700e0=f19
 KEYBOARD_KEY_700e2=unknown
 KEYBOARD_KEY_7002b=unknown

After that, simply run:

 sudo udevadm hwdb --update && sudo udevadm trigger

Make sure the settings have been applied by running evemu-describe:

 sudo /sbin/evemu-describe  /dev/input/event<id of your device> | grep KEY_