That Interactive Legend in Instant Apps is pretty neat. Wish you could use it in Experience Builder? Now, you can.
This Widget is designed to import the Interactive Legend Component used in Instant Apps. The Instant Apps Component library can be found here.
To use: Navigate to the folder in your terminal and run npm install --save @esri/instant-apps-components-react.
This Widget supports the Compact, Feature Count and Zoom To options from the Instant App.
As far as I can tell, it works by changing the symbology of the layer, it does not apply any actual filtering, so keep that in mind when building apps with this Widget.