Using the @ syntax for calling a variable in Arcade editor in Map Viewer Classic displays a warning saying: Variable is assigned but never used.

Additional Information

Workaround

Use template literals instead of the @ notation. For instance, instead of:

var P = Portal("https://wwww.arcgis.com")
var itemID='ITEMID'
var featureID=$feature["FIELD_NAME"]
Var FS= FeatureSetByPortalItem(P, itemID,0,['FIELD_NAME2'])
var Mathes =Filter(FS, `FIELD_NAME= @featureID')

Use the following syntax:

var P = Portal("https://wwww.arcgis.com")
var itemID='ITEMID'
var featureID=$feature["FIELD_NAME"]
Var FS= FeatureSetByPortalItem(P, itemID,0,['FIELD_NAME2'])
var Mathes =Filter(FS, `FIELD_NAME= ${featureID}`)

Steps to Reproduce