The queue of this id given to this user, null when it is not theirs — the screens ask
this one. Asking by id alone served any queue of the right entity to anyone who could open
the screen, hand-out lists and pinned filters included; the kernel's process queues are read
the same way, by id and user together.
Queues of one entity given to the user — personally or through one of their groups, the
same union the kernel applies to process queues. A queue given to nobody is shown to
nobody: there is no "everyone" shortcut here, as there is none in the kernel.