List string values from multiple related tables in ArcGIS Pro popup

Question

I have a polygon feature class (BIA tribal boundaries) with three relationship classes set up to relate to three separate tables, each with a 1:M cardinality from the feature class to the table. I want to configure the popup for the polygon feature class in ArcGIS Pro (not AGOL) to show the related data. I can do this for statistical data, like counts of the records in each table, but what I want to show is a list of values from selected string type fields in the related tables.

For example: I have selected the Ute Mountain Ute tribe, and the related records in each table are selected automatically. I configured the popup to show a count of the records selected in each table and also the string values I want to "list". However, the record count shows multiple records, but the string value only shows one value, selected at random from the table(s). For instance, under the "BIA Federally Recognized Tribe Table" heading in the popup, the record count shows 3, but only UT is listed as a state (should also be CO and NM).

My question is this: how do I configure the popup in ArcGIS Pro to list the string values from multiple records in a related table?

Using ArcGIS Pro 2.8.3.

Answer 1

An Arcade expression can be used in the configure pop-ups window. Using the "FeatureSetByRelationshipName" data function, which Returns the related records for a given feature as a FeatureSet. A possible expression is as follows:

var relate_fld = "FedRegistryName";
var rc_name = "BIA_LAR_7WesternStates_bia_entity_link_table";
var results = FeatureSetByRelationshipName($feature, rc_name, [relate_fld], false);
var output = "";
for(var rec in results) {
  output += "|" + rec[relate_fld];
}
output = Trim(output);
output = Replace(output, "|", ";");
return Replace(output, "|", "", false);

The last three lines attempt to clean up the delimiter, which is still not perfect (puts a semicolon before the list of values).