Tagging can have a number of meanings, so some of the answer depends on your approach.
Thanks so much for your reply! You have a lot of great thoughts. I’ll try to respond to each. The forum only allows two links for new users per post, so I’ll have to reply in multiple posts. 
Good point about “tagging.” Perhaps “linking” is a better term? Without knowing exact technical terms, by “tagging” I meant creating a hyperlink which links a word or phrase in the transcript of a document to a bio/glossary entry about that person (or simply to a list of other documents about this person/place/event). An example is found at the link below. In the transcription of this document, a click on “Chas W. Quiggins" links you to his bio page. I’m open to learning if there is a more specific or better way to refer to that function that I called “tagging,” since you make a good point that there are multiple meanings for that term.