For me - Generally I use my favourites like a bookmark for new species or mystery ones. I also fave first ids when I flag the taxon so that once the taxon is created, I can find it and then of course to not clutter my faves, unfave it.
I mainly favorite observations with really good photos / photos that I like, funny observations (like Mrs. Dave), and interesting observations (Vagrants, odd colors, behaviors, etc)
I have a google doc for any “useful” observations to go back and reference as needed so I dont need to favorite them. I also keep my other reference links there and have it organized somewhat.
I use this as a way to highlight selected observations that has a photo (or photos) and sometimes a great set of images that present robust markers (physical characteristics - morphological) to help with identification (ID) of species (and subspecies). Ideally, I aim to create a journal post and it is based on a calendar year format of selected observations that meet my criteria for capturing the markers with the intent of an educational process - for me and for others. Thus, I have that in mind when I fave an observation. Near the end of the year, I go through them (with some triage) and use it in an extended journal post to then narrate the “why” in the selection for ‘exemplar’ in identification. I think this can be useful as a way to use actual observations in a given year to showcase how others have added in to the “good example of images that help to ID” and then I highlight the markers. For me, the faved list will be centered on Mule Deer (as example - obs showing two or more markers: antler structure, ears, face profile, pelage, tail profile, metatarsal gland…etc). On occasion, the faved also represents the functional + the aesthetic + behavioral.