I've successfully used Arcade, in both Map Viewer and Map Viewer Classic, to develop pop-ups that pull data from a related table, using an expression similar to the one below:
Solved! Go to Solution.
The FeatureSetByRelationshipName isn't supported for symbology since it would have to query the related record for every feature being drawn. As opposed to just a single feature for a popup.
The FeatureSetByRelationshipName isn't supported for symbology since it would have to query the related record for every feature being drawn. As opposed to just a single feature for a popup.