Display full legend in AGOL app
Can you share your app or web map?
Are the layers turned off using scale dependency or do you want to have the capability to turn the layers on and off and maintain the symbology in a separate legend. I'd like to understand this workflow further to see if we have anything built in the software to enable this.
As a quick fix... You can always take a screenshot or image of your legend and embed it in the pop up (not super elegant, but it will work)
Example:
https://webapps.maps.arcgis.com/apps/GeoList/index.html?appid=7a778ed6062348e7acde8be1b2039c1e
<font size='2'>Legend</font><img src='https://webapps.maps.arcgis.com/sharing/rest/content/items/418c2b084f6e4b258762fcd001dd5e92/data' style='align:left;height:200px;width:195px;display: block;' /><font size='4'>Energy Tax Credits for {ZIP_CODE}</font>
Image URL
-Kelly
I can't show you the app but I want to have the capability to turn the layers on and off and maintain the symbology for all the layers in a separate legend. I considered the screen capture in an about panel, it will be plan B if needed. 
