Thanks! I now also added the @provider and @adapter decorators to my form and the configlet.
Edit: now that I have the form working, I wanted to try your GS approach with a single record, and see a typo that explains the traceback I had before:
<record name="restclient_connections" field="restclient_connections">
<field type="plone.registry.List">
<title />
<required>False</required>
<value_type type="collective.z3cform.datagridfield.registry.DictRow">
<required>False</required>
</value_type>
</field>
<value />
</record>
Should be: <field type="plone.registry.field.List">
But now, either using plone.registry.field.List or zope.schema.List I get a NotImplementedError from plone.supermodel
2025-06-30 14:48:43,950 ERROR [Zope.SiteErrorLog:17][waitress-0] NotImplementedError: http://localhost:8888/Plone/install_products
Traceback (innermost last):
Module ZPublisher.WSGIPublisher, line 181, in transaction_pubevents
Module ZPublisher.WSGIPublisher, line 391, in publish_module
Module ZPublisher.WSGIPublisher, line 285, in publish
Module ZPublisher.mapply, line 98, in mapply
Module Products.PDBDebugMode.wsgi_runcall, line 60, in pdb_runcall
Module Products.CMFPlone.controlpanel.browser.quickinstaller, line 544, in __call__
Module Products.CMFPlone.controlpanel.browser.quickinstaller, line 310, in install_product
Module Products.GenericSetup.tool, line 393, in runAllImportStepsFromProfile
- __traceback_info__: profile-collective.restclient:default
Module Products.GenericSetup.tool, line 1504, in _runImportStepsFromContext
Module Products.GenericSetup.tool, line 1316, in _doRunImportStep
- __traceback_info__: plone.app.registry
Module plone.app.registry.exportimport.handler, line 79, in importRegistry
- __traceback_info__: registry/main.xml
Module plone.app.registry.exportimport.handler, line 123, in importDocument
Module plone.app.registry.exportimport.handler, line 240, in importRecord
- __traceback_info__: record name: restclient_connections
Module plone.supermodel.exportimport, line 114, in read
NotImplementedError: Type collective.z3cform.datagridfield.registry.DictRow used for value_type not supported