Pop-up Arcade expression throws error when used for symbology

[udv1019]

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:

var tableRel = OrderBy(FeatureSetByRelationshipName($feature,"",["*"],false),'assessment_time DESC');

This pop-up expression can be saved w/o error and, along with other lines of arcade code, returns data from the related table. However, when I try to use that same expression (in a same map) in a Symbology expression, I receive an error and am unable to save the expression at all. Has anyone found a way around this strange restriction?

[Justin_Greco · Accepted 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.