If I am correct in reading plone.supermodel.utils.elementToValue (used by plone.app.registry import of registry.xml), there's no way to specify deletion/removal of a specific collection element. This is a bummer, as it means there's no declarative way in policy/profile to remove items from
plone.displayed_types (I don't want file, image in displayed_types, nor do I want to enumerate every single type).
What have folks used to work around? I am reluctantly (and with some grumbling) reaching for a programmatic import step via
plone.api.portal.set_registry_record, not sure what else to do.
I'm happy to hack plone.supermodel to give it element purge features for collection import, but I'm wary of breaking any other downstream consumers (outside of plone.supermodel and plone.app.registry).