Doing track stand while sitting?
I probably don't do "proper" track stands since I don't ride a fixed gear bike, but if you can find a bit of a hill at a stop then you can kind-of-sort-of do a track stand (you pedal up the hill and let gravity pull you back down). Sometimes the crown of the road is enough…

That said, I always sit, I didn't know you were supposed to stand, so I'd say keep working on it!