Mark messages as unread
Available on all plans
Cloud and self-hosted deployments
If you read a messages in a channel, but don’t have time to address them right away, you can mark that channel as unread. Hover over the channel name in the channel sidebar, select the More option, then select Mark as Unread.
Marking a channel as unread displays the channel as bold in the channel sidebar, and marks all messages in the channel as unread messages.