Several users on Twitter shared screenshots and videos of the new Backchannel feature in Clubhouse. It allowed for all participants in a room to chat via text, in addition to the live audio chat. Users got notifications from Clubhouse saying that Backchannel had been enabled and a new arrow button was showing up in the hallway.

source https://gadgets.ndtv.com/apps/news/clubhouse-backchannel-private-messaging-feature-rollout-spotted-users-screenshots-2469553#rss-gadgets-all