On my 2013 TDI, the trailer brake controller cable harness plug is visible by looking up through the opening on the left side of the steering wheel. It can be reached with your right hand without removing the lower panel. Reach up through the opening next to the firewall where the steering link goes through. It is however too short to pull down and you may need to remove the panel to plug your adapter cable into it. You can look to see that it is there without having to disassemble anything!