Status of Individual Forms in a Workflow

The Standard Application Report "Form Checklist" is powered by a Data Adapter that calls the FormsStatusForWorkflowUnit Method.

That might be enough to create the report that you mention - with a caveat: in my tests, that method does not return any forms that have never been touched (i.e. it will only list forms that have been marked as completed or rejected/reverted).

If you need all the forms in a detailed manner, you might have to get your hands dirty with a business rule. Start from BRApi.Forms.Metadata.GetForms(si, workflowClusterPK), it will return a XFFormsForWorkflow object that represents the "Forms" item in the profile (note that the PK you pass should point to that Forms step, not to the period). That object will have .OptionalForms and .RequiredForms collections containing all forms, including untouched ones.