LED brake/tail/marker Q

I have JCR upper 1/4 armor with the tail light boxes. I ordered 4" red brake, 4" white LED for backup and a 2" side marker light. I am wondering how I can make my 4" red LED work all three functions (brake, directional and marker. I have brake and directional working and I want to somehow wire my marker light to the brake.

If I can wire in some kind of resistor to bleed some of the power, I should be able to just illuminate just the 4 inner LED's as a marker. Sounds easy enough. Anybody ever done this?

I was hoping to avoid needing a 4" orange/amber marker & directional. Ideas? Thoughts? Not sure if I need a trailer harness box I've seen. Right now everything works correctly, but I just don't have a rear maker.

Thanks in advance...