If you're the chat owner (you created the Room or Group), you can delete any chat messages posted in the chat by hovering over it and clicking the trash bin.
To delete your own chat message(s) anywhere in Rabbit, hover over the message and click the trash bin. You can also edit by clicking the pencil icon.
To clear the entire chat (Room or Group chat), click on the drop down at the top of the room chat. Then Clear chat history.