Saw @RPGIS's idea for ArcGIS Enterprise and thought I'd add the idea to the ArcGIS Online too.
The ability to use Arcade expressions for filtering data in ArcGIS Online's Map Viewer would be extremely useful. We already have the ability to use arcade for symbology and pop-ups, but filtering has been left out.
A simple use-case for this would be checking to see if the CreateDate field is within the Current year. This is easily achievable with Arcade with IIF(Year(Today()) == Year($feature.CreateDate), 'YES', 'NO'). With this I could make it so my map is always showing relevant information, but instead I have to change the year on the filter manually every January. Lots of other use-cases become possible if Arcade Expressions are allowed in map viewer.
