If you mute the channel and then configure slack to only show starred rooms and rooms with new messages, you can achieve this effect. The room will stay hidden

If you mute the channel and then configure slack to only show starred rooms and rooms with new messages, you can achieve this effect. The room will stay hidden unless someone says something, at which point it shows up in the list, unbolded. This lets you know to check on it at your convenience without triggering any of the notifications.