Certain forms are already smart enough to know where the cancel button should take you. For example if you navigate

My Population > edit a person > Add an Identifier

or

Organizational Identities > edit a person > Add an Identifier

either way you end up at /registry/identifiers/add. However, the form knows from the presence of an orgidentityid parameter or copersonid parameter where to send you back to if you click cancel. Make sure this works for all cancel buttons.