I was at my dealer yesterday looking to do the same thing. I have a 2018 Ram 2500 Bighorn Harvest Edition. My top row of buttons is all full- hill descent control, traction control, tow/haul, engine brake, and front/rear parking sensors. Bottom row is just heated seats and steering wheel, with a couple of blanks. I already have controls for the seats and steering wheel in the touchscreen, so I was ready to give them up so I could have a full bank of operable aux switches.
According to the service guy at the parts counter, it can't be done on my truck. FCA does not make a harness that will not only link the switches to the aux fuse block but also accommodate the no-longer-used leads for the seat and wheel heat controls and then interface correctly with the BCM.
Now he did say that those leads could possibly be jumpered, but the harness kit for the aux switch bank was still lacking a few leads. What they have now is not the same as what the had offered in the past; no surprise, but Ram's plan is to force buyers into all of their options from the factory with as little possibility of doing it after purchase. And of course, while an enterprising DIYer could likely make it happen, it all runs the risk of running afoul of the almighty Warranty.
