you can adapt the same idea from https://forum.inaturalist.org/t/bulk-selection-of-observations-to-add-to-a-project/1747/70 (and subsequent posts in that thread).
i didn’t do any testing, but based on the API documentation, the core required request would be something like:
curl "https://api.inaturalist.org/v1/identifications" -X "POST" -H "Content-Type: application/json" -H "Accept: application/json" -H "Authorization: %jwt%" -d "{\"identification": {\"observation_id\": %observation_id%, \"taxon_id\": %taxon_id%, \"current\": true, \"body\": \"%comment%\"}"
(i assume body and current are optional, but i didn’t test.)