Web Map Legend - only show filtered items or items in view extent

[AutumnMason]

Not sure if this has been mentioned before, but I would really like to be able to use the same function that I am able to use in ArcGIS Layout View, where I can check to only display items in the TOC that are checked, or to only show items that are in the map extent. Right now in a web map, even after I filter, all of the items still show in the TOC and legend. I can somewhat bypass this by dragging all of the icons I don't want to show up in the legend of a web map/app under the Other option in the Change Style (Unique symbols) menu, but with over 30 items, this process is cumbersome.

For example, see pic. If I only want to show Campground Camping, I will have to move all of the other legends under Other so that they don't show. Is there a better workaround than what I am using? Or can this be added as new functionality?

Thanks

[KDCGIS]

I'd regard this as a necessary feature.  For feature layers used differently in different maps/apps we need to have flexibility in what the legend shows.  We can workaround for my current map at the ArcGIS Pro level/adding a more customised service, but to me AGOL needs this functionality.

[RobertKirkwood]

Can this be done in JavaScript using the Legend widget? 

[BenLeslie2]

I am also trying to filter the legend by map extent on ArcGIS Online (specifically Dashboards and/or Web App builder for developers) - was there any progress on this?