I started with this Ender 3 led strip : https://www.thingiverse.com/thing:3105878 but with the strip being directly above the X carriage, the nozzle was always in the shadow, making it difficult to inspect while printing. I therefore designed these side strips. They can easily be attached to the top extrusion with a T-nut. Designed to add a 15cm led strip, with hole on 3 sides to route the power wires.

Printing:
The best way for now seems to be printing with the LED side down, with supports.