Wiring harness question

Have a 2010 Jetta sedan and putting a 2014 Jetta sedan engine and harness assembly in for replacement. The 2010 has one extra connector on the harness that the 2014 harness doesn't have. It connects in the LF, just under the headlight, 3-4 wire, 10 pin connector. Is important? What is it for? I have a couple pictures, but haven't figured how to post.

The 2014's NCS harness is going to be different than the 2010's A5 harness. The ECUs are not even in the same place.

Will everything be ok if I just change the harness?

Check the coolant plumbing, specifically the crossover pipe and thermostat housing (buried under the intake). If those are the same, then I think you should be able to just change over your harness. If not, the BLOCK is different, and you'll need to change more stuff, or get a different (correct) engine.

The NCS and A5 are very different cars, so lots of items are not going to be the same.