There are years of posts on how to hang clothes in Models S & X, but I'll add to them for the first time here, as my solution differs from most.
If you look at the lower back of the second-row seats, you will find the slit in the fabric that provides access to the child-seat strap anchors (these are not the LATCH anchors - those are in the front, hidden in the crack between the seats' horizontal and vertical members).
I take TWO of the +/- 6" long bungee cords that each form a single loop with a plastic ball joining the two ends - very common items; I cannot provide a photo this morning so I hope that description suffices. One gets looped through that anchor as described above; the second is ganged to the first.
When you need to hang clothes, reach behind the seat and grab the loop, stretch it up to the seat top and snag your clothes hangar with it. The two bungees I suggest provide just the right amount of tension to keep 1-5 or so items suspended near the top of the seat back. You don't want too-strong or -weak elasticity, for obvious reasons.
When you want to make this set-up disappear you can stuff the two bungees below the seat back. Our Model X has the fold-down seats, which makes this a zero-hassle operation.
This works really well for multi-thousand miles trips. I'll try to snag a photo or two later in the day.