Use the trade offers attachment. You can send trades to a friend or neighbour individually, or a group of players. Just put the trades in the market and then attach them to your friends or neighbours.
That indeed is a great feature!
But that is only for sending one's own trade offers. It has no function when we search trade offers from a particular player. Some players tend to be generous and instead of looking for a certain type of good, we may also look for "sale" opportunities. This is only one example for why we may need to find a certain merchant.
I have wondered for a long time why there is no search bar in the trade window. It could at least have a filter option for the status bar (offer - need - merchant - rate) where we could filter names/rates from A-Z or Smallest-Biggest type. Even that would be a great help to find who or what we are looking for.