One button per person
When this option is on, the list window will not display multiple
buttons for people who are logged on at more than one place.
Instead, their location menus will
change to display all of their locations.
This is actually the same option as the snapshots window's One button per person
option; turning this on turns the other one on, and vice versa.
Here's a normal location menu:
And here's one with the one-button-per-person option on:
Back to the List Options dialog page.