I would like to write an Arcade expression to generate a unique next sequence number in a feature class. which needs to compare two feature classes and generate unique number which is not included in either of feature classes.
You can use Max on a featureset, this would get you the highest number in each class, and then increment by one
https://developers.arcgis.com/arcade/function-reference/featureset_functions/#max
Is there way to list all field values, display in console and pass them to array ?