Presently, the only Search filter is document type. Being able to search by filename or partial filename would return more specific and more useful results.
The problem with search-by-content, which is the only search option Dropbox offers, is that it often yields an unmanageable number of results. It can only be narrowed by document type, such as PDF, DOC, etc.
Windows File Explorer offers filters such as filename and date-created. Having Dropbox be able to filter search by filename (and date) would be a tremendous time saver.