What Is the Difference Between Add and Remove Logic for Iterable Preference Centers?

ADD is read/write. It reflects the current state of the User on page load. Then, based on whether the checkbox is checked, it adds or removes them from the given List or Message Type on Submit. Add is the option we recommend for all checkboxes besides unsubscribeAll.

REMOVE does nothing on page load, as if it isn’t there. This option only removes the user from the List or Message Type on Submit.