We don't have an option for muting alert now. Can you give a usecase where mute is needed?
As an alternative you can use 'Downtime Notification Delay'. This setting which is available in Notification profile will help you avoid alerts for a certain period of time.
Admin -> Configuration Profiles -> Notification Profile is where you will find it. Once this is set for the monitor you will receive a notification only after the configured delay.
Product Manager, Site24x7