Once clicked, the who's here button in the Control section, will show the user(s) who is in the room.

The user(s) will be shown in alphabetical order and will have a green star next to them if they are your buddy, or a yellow star with a question mark next to it if they might be your buddy later.

The who's here button used to automatically show up once you enter a different room. Now it's the tab you've clicked before entering another room.