This is the “combine” tutorial; the opposite situation, the “split” tutorial, is here: https://forum.inaturalist.org/t/how-to-fix-your-observation-with-photos-of-multiple-species/15096
Since the word split means something in taxanomic curation, it actually is not that helpful of a term to put in the forum search box. I see your point though. Unfortunately the author of a post (me) cannot edit it after too much time has passed. Perhaps a forun mod could change it to “How to fix your observation with photos of multiple species: splitting an observation”