In the top right, there is a search symbol, along with another small arrow that brings up another drop-down menu. At the top left of a particular chat, you'll see their name and when they were last online if they have this feature activated. There are also more options in each individual chat.
Alternatively, you can use the keyboard shortcuts below for that. You can archive a chat, pin it, mute it, delete it or mark it as unread from here. Hovering over each individual chat in the main screen will also bring up a small arrow for that particular chat, offering a couple more options.
