I changed the default project filter of my kanban board from the board settings (General and Filter settings) to be:
project in (A,
ORDER BY Rank ASC
to be able to see issues from A and B in my kanban backlog. The issues from A and B are shown in the query result, though I can see only the original issues from A and nothing from B in the Backlog. Project Browse permissions in B are set to application-access and even to Anyone. So I don't get why issues from B are not shown in A's backlog.
Best regards