Add a child case type to your application to extend your case type hierarchy and modularize the way that you model work in your organization.
You can either reuse an existing case type or add a new case type to define a parent-child relationship. Add a new case type when no existing case types meet your business requirements.
Before you add a case type to your application, review your existing case types and case-type dependencies. Although reusing a case type saves time and effort, it can introduce unexpected complexity when a top-level case type is demoted.