Optional persistence features can be added as child components of type EPF_PersistenceManagerExtensionBaseComponent to the EPF_PersistenceManagerComponent. They provide an easy way to hook into the persistence world setup process to prepare/restore additional features that might not be needed for all game modes.
The persistent door state manager allows to persist the open/close state of doors on the map. By default all doors from all buildings are saved if they are not in default position (closed). Optionally a EPF_PersistentDoorStateFilter can be configured in the attributes to e.g. only track doors that are near a base building territory or certain villages on the map.
The door states are tracked through the SCR_DoorUserAction. If you have custom scripted mechanisms to open and close doors, consider adding a call to EPF_PersistentDoorStateManager.UpdateDoorState as demonstrated in the modded action.