A direct message or a group conversation can be muted from its row, its menu or its details, for a while or until you unmute it. A muted conversation is dimmed, sends no notifications or emails about missed messages, and is listed under Preferences › Notifications › Conversations you muted.
At the largest text sizes, search results start with a result, list rows keep their names on two lines, Link keeps Mute on screen, and to-dos keep their words beside the bell. With your phone held sideways, page headers fold to one row, K Buddy keeps the conversation in view and Canvases become a compact list.