Scratchpad is the 'Design Mode of the Health Monitor'. Through Scratchpad you can design and configure:
Collector Managers
Collectors
Event Sources
Connectors
Event Source Servers
You may right-click on the Sentinel icon and add the components. For more information, refer to Adding components to Event Source Hierarchy.
NOTE: You cannot view the status of any object in the design mode as they are not connected to an instance of a real Collector Manager.