There are filters for Due Date, Received/Received Date, and Retrieval Date.  When I need to Publish Requirements, it would logically be extremely helpful to search either on the Publish Date ("is missing") or Requirement is NOT Published, along with the Due Date (already available in filters).  The only way to search on Publish Date is in an Advanced Search, which is really unfriendly.  Please, I beg you, add a filter to search on whether a Requirement is published yet.