My use case is checking to see if all 12 forms have been filled out at a location. I have relationship classes that ties them all together. I can check for 0 counts or even look for a pattern of 1-2-3. For now it only works in the browser.
I could also do some of this using the built in relationship pop values but those do not work either. I have posted about this issue several times over the last year or so.
Then what I would really love is if they all worked offline without having the sync 123 to Collector but that would require the new 123 API prob. We would like them to get a message before they leave the sample site since, once they leave, it is too late. True app integration is the next step I think. Imagine loading a TPK once and using it in all Esri apps (vs having the same TPK on there 3 times).
Access to the relationship classes in Arcade would also be nice. The only reason i really need FeatureSet in the first place is to simulate a relationship class lookup with a query. I think relationships classes are a great part of Arc products but it seems to get very little support.
Thanks for looking at it.