The search parameters for submissions are Title, Author, Editor, Reviewer, Copyeditor, Layout Editor, Proofreader or within a date range for when a submission was submitted, copyedited, layout edited, or proofread. There's no feature for "tagging" articles. Also, OJS is designed to have the author agreement digitally signed during the submission process, so I doubt whether an enhancement request to accommodate this would be of interest to the OJS developers, though you're certainly welcome to submit such a request.
Electronic Publications Manager
Office of Scholarly Communication and Publishing
University Library System, University of Pittsburghvgabler@pitt.edu