Identifier claims attach a registry id to a profile. Node 1 is the author website (https://www.wikidata.org/). Node 2 is the human or group the identifier describes.
Open Create on the quote page to search an existing profile via autocompletion. If none is selected, the form first POSTs /human-profiles (quote-attached), then saves the identifier against that new profile id. Dummy identifier rows stay in API memory until the backend table ships.