Reference Coordinate System
The Ref Csys element allows you to change the reference coordinate system, which is used as a default datum for the Verify step. The Ref Csys setting is modal, that is, the reference coordinate system from the previous step will be automatically used unless you explicitly change it. If you create a new coordinate system by clicking Inspect > Reference Coordinate System, it will automatically become the default for subsequent steps.
You cannot create reference coordinate systems "on the fly." In order to change to a new coordinate system, you have to create it using the Reference Coordinate System option prior to creating the Verify step.