Traditionally (and roughly) dictionaries are written by teams of editors who gather large corpora, identify new words or new word usages, examine how those words are used, and then assign parts of speech and write definitions based on their examinations.
With no ill will meant toward dictionary editors, this seems a task well suited for computers. (As an interesting aside, see this anti-capitalist critique of automation.) Google and Apple, especially, have troves of written material, both old and current. It seems to me (and I confess I have no computer background) this could easily be used to largely automate dictionary writing.
Computers can identify which words are used, in books, emails, texts, etc, which are yet undefined. By comparison with other words used in similar contexts (its location in sentence structure, the meanings and parts of speech of other words which appear in the same place, etc.) the computer could create a list of likely synonyms and assign a part of speech. A human editor would probably then still need to write the definition, but the bulk of the work is done.
Are dictionaries doing this? In some ways this is simply glorified text-prediction. I have looked online but found nothing. The problem with searching for information regarding dictionaries is that every result is a definition.