Implemented as part of the work on AutomaticIndexingSynchronizationStrategy in Hibernate Search 6. See https://docs.jboss.org/hibernate/search/6.0/reference/en-US/html_single/#mapper-orm-indexing-automatic-synchronization

We don't have per-index configuration yet, but theoretically that shouldn't be too hard to implement. Anyway, I don't see a use case for that right now, so let's open a new ticket if we come up with a use case.