Did you buy the vehicle new? If so, have you ever had service or a third party install an accessory for you?
From the service manual some possible candidates:
1) Under the seat there is a puddle lamp, there is a connector that looks similar (see step 8):
Model X Service Manual | Tesla
Also in the rendering in step 6 here:
Model X Service Manual | Tesla
If you don't have working puddle lamps, that may be it.
2) In step 19 for the 1st link, there is a seat belt buckle connector that probably is for seat belt sensing. If it is disconnected however, I imagine there would be errors.
Refer to the manual for full instructions, but looks like you can access it by unscrewing a screw in step 13, before popping the RH side shield in step 14. Given your seat is still right next to the center console, it might not be possible for you to pop open the shield however (the Tesla instructions assume the seat have already been removed from the car).
If however you haven't been having any errors or problems related to the seat belts, I wouldn't go about trying to connect things. It may have been disconnected on purpose from factory.
You can also put in a service request in the app to ask about it. You probably have to take far better pictures however. The ones you took make it very hard to identify what type of connector it is (for example can't see the pin(s)), as well as the relative position of the connector on the seat (will need a wider picture for better context, and also a picture following the other end of the cable to see where it leads to).
