upstream/downstream Reference
You can filter items by their references.
For example: All task that have release reference which is In Progress state.
1=Task tracker id
31=Release field id
2=Release tracker id
tracker.id = 1 AND 'upstreamReference.31' ={'2.status' = 'In Progress'}
You van use shared fields :
1=Task tracker id
2=Shared field id
tracker.id = 1 AND downstreamReference.cbQLGlobalType.2 = 'Item'