Sitting pad for when you are glassing and to use as a doormat at the tent. I use 1/2 a z-rest pad.
Some sort of back support chair like a sling chair for use with trekking poles, or a prop your pack up on the poles to use as a back rest.
If you use a Hilleberg bring a towel to wipe the inside with. You will likely get rained on from the condensation. They are wet tents and don't vent well. At least the Nallo and Akto I used were.
A basic sponge works for inside a hilleberg too. Easy to just squeeze it out when you’re done and weighs nothing when it dries.