In Order Entry Ship to Addresses column editor,when you double click on the top to bring up the list of available search fields, there is one named "filler". What is it and where is it accessible to put information into it?

This is my problem. We have a few accounts with a head office and multiple ship to addresses. There may be a different sales rep for the ship to addresses than the default set up for the head office. I am looking for some way to enter the sales reps info into the ship to addresses so it is readily available to change the default sales rep when entering an order/invoice. Any suggestions?