Not sure if in your mk6, but in mk5 jetta (not all of them) and in both my 2015 GSW and Passat, there is an electric aux heater.
In mk5 the heater would communicate with VCDS with its own control module. In the mk7 GSW it's called PTC heater and I could only find it when I looked at the HVAC coding. Still investigating where in VCDS for the 2015 Passat.
This electric heater is installed right next to the heater core, I read some mk6 wagons have them. If you undo the side trim by the accelerator pedal (one T20 screw) the heater core will be right there behind it towards the lower center dash, and in front of the heater core, there will be thick wires going to it, like in this post:
Moved the wife's car yesterday 2015 tdi se wagen and noticed a strong plastic/electric burning smell coming from the heater vents. I did a scan with the vag com and it did have some heater box codes. I'm assuming something with the aux heater melted and is melting or the harness to it either way...
forums.tdiclub.com
Make sure if you do have the PTC heater, that is working correctly, and read up on how it comes on: max heat, 4+ speed, and foot+defrost.
Others have said remote starters are useless, as TDIs can idle forever and never create enough heat for the cabin.