The only one of those ‘extra’ columns that is available for all document filetypes is the Spotlight Comments column, which can be added via View > Columns > Spotlight Comments. If you used the suggestion about to store citation information in the Spotlight Comments field of the Info panel, at least a portion of the citation information would be available in this column. If the citation information is long, it could be viewed while the document is selected if Shift-Command-I is pressed.
The others that you noted are those in Document Properties (Tools > Show Properties), which are editable for only a few filetypes, and not universally editable even for PDF or text documents.
My own preference for adding metadata such as citation information and notes is to create an Annotation note for the document (Data > New from Template > Annotation – a keyboard shortcut is shown). The Annotation note is linked both to and from the referenced document. Annotation notes work for documents of any filetype, and are searchable.
AHA! Annotation notes sound a much better solution, although I really would like to be able to find all documents by a specific author. I’ll figure that out another day, I guess.
Thanks! I wasn’t aware of Annotation Notes so this was really helpful.
They are active and editable in Tools > Show Properties… for document types that support these metadata. For example, when a PDF is selected one can edit Author, Title, Subject, and Keywords in Show Properties… If you were wanting to edit all of a PDF’s metadata you’d need to use Acrobat or some such app.