It seems like everyone has a multimaterial printer except for me, as every keycap I found for the BTT HBB button board has multiple pieces to form inserts. It was pretty frustrating.

I instead created a part that is only one piece, but then was upset about not being able to see the beautiful LEDs I programmed, and here we are. Clear PETG filament also works great to be able to diffuse the LED / act as a lightpipe.

Two Options:

• Dot - Insert a piece of clear filament into the hole and snip off the excess. The hole is modeled 2.2mm and it is still a tight fit with 1.75mm filament at least on my printer.
• Bar - Cut a 6mm long piece of filament and cram it on the hole sideways. It is a good idea to sand the PETG a few strokes before cutting it to rough it up and better diffuse the light.

I've attached my klipper HBB config as well. The LEDs only come on when the buttons are pressed and turn off after 0.8s.

• Z-adjust +0.02mm / -0.02mm
• Preheat: PLA, PETG, ABS. Pressing the same button again will cycle through extruder temperatures 160C, 205C, 230C, Off
• Start / Cancel Print
• Everything off