If you have a chat room that is no longer being used, you can unsubscribe it.
Click on the context menu icon next to the chat room (or just right-click onto the chat room).
Choose the option Move to Archive
Archiving a Chat room
The selected room will be moved to the Archive tab.
Chatrooms contained in Archive.
Of course, items in the archived rooms can be restored later, when needed.
Go to the Archive tab folder and either click on the context menu icon, or right click onto the chat room and choose the option Activate.
The selected room will be activated and moved to the list of your rooms.