This or some similar functionality would really help in linking interactions between species, as at present such interaction fields can easily get out of sync and show an entirerly different species than was determined in the seperate observation for the associated taxon.
It’s not the same thing as grouping or linking observations, this is about obtaining the taxa of another observation dynamically and having it appear on the observation page. There is a field called “Associated Species with lookup” that allows you to select the taxa that your observation is interacting with, but if you don’t know that taxa, or if it gets an ID correction from someone else (via a different observation), then the taxa in that associated species field doesn’t get corrected. You can group associated observations as per that discussion, but it won’t show the associated taxa dynamically in the observation you are looking at, nor will the associated or interaction taxa be accessible from a data extraction perspective.
The linking talked about by @KitKestrel seems to be a more general concept. I see that request as talking about grouping observations, this request is about having a field that dynamically updates depending upon the community ID of another observation - linking/grouping might achieve some of the benefits, but it is a different idea. The ideas expressed by kueda above are also not quite the same thing but certainly get to the heart of what I am proposing, and take it to a more sophisticated level :-)
(What I am suggesting still requires that there be two observations from the same photo, which at present requires action by the observer to duplicate the observation, which is problematic if they are no longer active. A more general implimentation of interactions might bypass the need for duplicated observations, that would make this request redundant.)
Slightly different to the request here, but having an observation field type of “observation” would help. For example I have two observation (https://www.inaturalist.org/observations/48873155 and https://www.inaturalist.org/observations/46345544) where one species was observed to kill and eat the other. I found the Observation Fields “Interaction->Preyed upon by” and “Interaction->Preyed on” but that means I need to know the other species, which I don’t and anyway can change as others add identifications. So a better way is to just tag the each other observation.
So I created two new observation fields which ask for the Observation ID instead but since there is no field type for observation ID these are just numeric which mean they don’t auto-link etc.