I need to know how LED status lights like these on my Bose Q35 headphones, are made? Is it a light guide? some kind of foil or what?
They are known as LED Guides They are specially designed structure with mold such that led light attached on PCB will be directly guided to upper surface with approximately full intensity.
LED guide is the small pipe like structure not more than 4-5mm long and 2-3 mm in dia which got directly cover the led on PCB when PCB is placed in enclosure. You can ask any manufacturer for this type of guide.