The register of deeds of any county having a population of 750,000 or more who has copied a document by microphotography, microfilm, optical imaging, or electronic formatting that is accepted by him or her for recording or filing shall also, as a substitute for marginal references required, prepare an index for documents of ancillary nature for which marginal references are required. The register of deeds shall prepare and maintain the index for ancillary documents to show the document number and, if given, the volume and page of the original recording or filing plus a record of any recordings or filings affecting or pertinent to the original recording or filing requiring marginal references subsequent to the date on which the county begins recording or recopying by microphotography, microfilm, optical imaging, or electronic formatting.