I may be wrong, but it seems like there is no way to convert an existing, non-confidential queue to confidential. (Maybe I'm overlooking something obvious though.) There may be cases where this one-way increase in confidentiality is needed without having to destroy and recreate the queue.
I think that the reverse action, converting confidential to non-confidential, should remain unavailable.
I may be wrong, but it seems like there is no way to convert an existing, non-confidential queue to confidential. (Maybe I'm overlooking something obvious though.) There may be cases where this one-way increase in confidentiality is needed without having to destroy and recreate the queue.
I think that the reverse action, converting confidential to non-confidential, should remain unavailable.