It would be great to let Arcade access information from related tables. For example for a popup, if you could click on a feature and use Arcade to loop through records in the related table and display that information. @ Kelly Gerrow BPriya K
I vote for this idea
An example use case is the Restaurant Inspections Collector template, you can have Arcade find the most recent related record so you can symbolize the Restaurant by the latest grade.
Or any Survey123 form with repeats - the field apps make heavy use of related records and actually using them in the ArcGIS Online/Enterprise ecosystem is currently difficult.
Part of the functionality is available in ArcGIS Online after the update of December 5th. Kelly Gerrow just published a blog about this: Overlapping Features in Pop-Ups Quick Introduction to Using FeatureSets with Arcade . This addresses accessing data from a different layer and performing an intersect to show this data in the pop-up window. In a blog that I published (in Spanish, sorry) the second example shows how you can access a table (that does not have to be related using a relationshipclass) and do some statistics on it:
Mejoras en Arcade en ArcGIS Online con la Actualización de 5 de diciembre del 2018
There are a couple of limitation:
A little more details in this post: Using FeatureSetBy functions in Arcade to drill-down to other layers and tables
What a great idea! Huge potential in here. I'd vote up a 100 times if I were allowed to ;-)