I installed the cartrim hatch light today. The install is actually way easier than the video on cartrimhome’s website. All you actually have to do is pop out the light placeholder, pop out the control panel for the tailgate, connect to the wire harness there, fish the wire over a few inches to the left and install the new light. Literally takes 5 minutes. Highly recommend. The video on their site was shown with a vehicle without an electric tailgate which is a bit bigger job.
So I have the unit that you have - for the power tailgate. Is all the power for the left side light supplied from the right hand light?