The ArcGIS Online / ArcGIS Portal map viewer allows Arcade expressions to be used for symbology.
The ArcGIS Online / ArcGIS Portal map viewer allows Arcade expressions to be used in the popup.
If I want to use the same arcade in both the popup and for symbology for the same layer, I need to manually duplicate the arcade expression - ie write it again in the symbology configuration even though I have already written and saved for the popup configuration.
Perhaps it would make more sense to have the arcade expression written for the popup to be available to the symbology dialog and vice-versa rather than having to rewrite the expression?