Hi there!
I just completed a build of the MB6582, and during construction I designed a small PCB to neatly hold some backlight LEDs for the rotary encoders.
The PCB source files and installation details are all available here on my GitHub page, licensed under Creative Commons so that anyone is free to order their own or change it: https://github.com/dwhinham/encoder-backlight-pcb
I have about 9 spare sets of 15 PCBs if anyone would like some.
Shoutout to @Hawkeye for the inspir