Curtains while camping are essential.

They need to be heavy or lined with Reflectix, for insulation from sun and cold.
They must be opaque, for reading at night sans audience.
They need to be easily removed and stored. (where?)
They could be pretty.

This fancy hint below came from a person redoing an old pop up trailer.

Next curtaining area is the tailgate end. When the tailgate is down and the cap hatch is open I would like to hang a bug screen in the summer and a rug/blanket in the winter. The  simplylivingandsimpletravel suggestion is perfect:

 …one can put up a rod/dowel above the door and using large curtain hoops, hang a blanket or long throw rug in front of the door. This can help quite a bit with cutting down the draft, probably more so in older rigs. I know it works.

Two items to hang, a no-see-um proof screen and blanket. I can imagine that the screen would need something at the end to keep it hanging straight down, not waving in the wind and admitting mosquitoes and horseflies and gnats. Needs to be a way to open and close for ingress and egress. Rolling it up ? Hanging it up?

This sounds like a great project  for on the road. Sitting in some out of the way, hidden spot,  sipping on Tokaji, figuring out the logistics.