G502 series missing reprogrammable buttons

Hi, first of all thanks for this great piece of software!

I noticed that I can't reprogram the buttons on my G502 X Plus mouse. At first I thought I'm missing something, but looking at the output from solaar show and at the file at docs/devices/G502 X PLUS 4099.txt, it seems this is indeed missing. I also checked for the older models of the G502 series, but it seems all of them are missing their remapping. Is this a missing feature or a bug? I'd love to help, but have no idea where to start or how to do so.