Sometimes, alerts or notifications are not helpful. You want to see them never again. You can adjust the source not to send the events in the first place (such as tweaking the EventBridge rule or CloudWacth alarm). It might be easier to press the mute button. After pressing mute, you will not see similar alerts or notifications again. Similar in the same way that is used for aggregation.
You can unmute all alerts and notifications in a channel. Send a message in a channel mentioning @marbot:
@marbot Unmute all!