Unless my character is a big bruiser, I bring a cow of burden when fetching goods for trade with traders. I then pull everything off the cow (which takes no time) and stands immobile while trading with the first trader (or several, if they happen to be in range). When done, I drop the inventory on the ground and push it back onto the cow, and then continue on to the next trader.
To keep track of them, I tend to ask them their name only in direct conjunction to trading, or, if I've encountered them while out and return with goods, I talk only to the ones who have interesting goods, so only the ones with names are of trade interest.
In the former scenario, the ones with names have already been "processed".
I agree, however, that it's a pain to keep track of them, in particular in spruce infested forests.
One might think that the traders would flock around you to peddle their wares, though... But, as mentioned, it would require a change to initiate/finish trade, as well as handling the case where the ungrateful customer just runs away in the middle of the session.