Often when configuring markers you will need a "reverse" marker that displays when the metadata in a certain field has changed. Cloning markers is an easy way to achieve this.
In the list of Markers in the site configuration, simply hover over the marker you'd like to duplicate and click on the Clone link. The cloned marker will be added to the bottom of the list, and you can easily modify it by clicking on its Edit link and changing the settings for the marker as needed.
Markers can also be deleted using the Delete link that appears when hovering over a marker in the list.