Depending on the rule's state, the Rule Definition tab gives you buttons to:

• Checkin changes to a rule
• Checkout a rule that has not yet been published
• Unlock or Checkout a rule that has been published

Learn more: Checkout, Checkin, Locking, Publishing, Versions

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The gear icon also gives ​you the option to:

• Test the rule

In the sidebar, you:

• View and edit the input and output data components of the process definition.
  When the rule is invoked, the designer maps data from the calling context
  to the rules inputs, and maps the rule's outputs to that context.
• Create and edit integrations

In the main panel, you:

• Edit the process definition, the same way you edit a stream process. 
• Add Gateways and Endpoints, the same as for a stream process
• Add ​Smart Steps to the process:
• Transform data by updating fields directly, or by using a decision matrix
• Invoke an integration service
• Generate errors and execute actions, conditionally or unconditionally
• Invoke a subrule
  
  

To add a smart step: Click Smart Steps and drag one of the icons that appears into the diagram.