ArcGIS Online Map Viewer - style a polygon Outline with a color Ramp

[AndreaB_]

I would like the ability to symbolize/style a polygon Outline with a color ramp in AGOL Map Viewer.

We can do this in ArcGIS Pro. Best I can do in Map Viewer is make the fill transparency 100% and then pick one color for the outline.

From AGOL Map Viewer now: 

Thanks.

[MarkPatrickBank]

I was just looking for this option, myself. Having several overlapping polygons, fills are too clumsy for my usecase. I was hoping to distinguish them with their outline color.