If a chat is very active and resulting in a lot of notifications you’d prefer not to receive, you can mute it.
Click a chat's More Options button in the list pane.
Select Mute.
The chat icon changes to show that it is muted. New messages in this chat will still appear in the chat itself and in the preview in the list pane, but you will not get notifications anywhere else.
Click a chat's Unmute button, at the top of the chat, to unmute it.
When a chat is unmuted, you will resume getting notifications from it.
When you are done with a chat and do not need it appearing in the recent list anymore, you can hide it.
Click a chat's More Options button in the list pane.
Select Hide.
The chat is hidden and will no longer appear in the recent list. If more messages in that chat come in, though, it will reappear. The message history will be saved as well