Makes no difference, because then I would need a list of these persisted configuration objects...

I thought placeholders would be able to fetch their own configuration 🤷

It's not the fetching, that's the problem. To create a new placeholder of a certain type, I need an admin class for SonataAdmin and that will need a referenced entity class. To get a selection of possible placeholders on the admin backend to create a new entry, I need a list with these entities (and there admin class, but that's not important right now).

Also, this is not our only bundle that is affected.

this looks like a use case forContainerBuilder::findTaggedResourceIds that exists in Symfony 7.3, if the goal is to identify things that are meant to be excluded as services.

OK, that's fine for Symfony 7.3, but that doesn't help in Symfony 6.4, where this feature doesn't exists. Will this be backported? Because without it, the changes to doctrine-bundle to exclude Entities are without a resolution, as far as I understand it.

Also, is the CompilerPass the only way to get the list, or do the tagged iterators work on resource tags?