Creating cross-store relationships

I am trying to use fetched property in store A to acess data in store B.
In the core data documentation there is a reference to this capability :https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/CoreData/HowManagedObjectsarerelated.html#//apple_ref/doc/uid/TP40001075-CH17-SW13

I am a little confused though since the fetched property I created askes for a destination entity and only entities from store A are selectable.
How can I make it so that I can set an entity in store B as a destination for a fetched property from store A?



My problem is similar to this one: https://stackoverflow.com/questions/8209932/cross-store-weak-relationship-with-fetched-properties?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa
Thanks in advance!