Forum thread: https://forum.shopware.com/t/zusatzfelder-fur-eigenschaften/64068/7
Issue Ticket that is "solved": https://issues.shopware.com/issues/NEXT-3710

We need custom fields support for property group options. That was possible in Shopware 5 according to the linked issue ticket.

Also, the issue ticket asked for property_options specifically and the ticket was marked as solved without adding custom fields to those.

Please add that missing feature.