A recent blog article on Esri Story Maps Developers Corner illustrates the ability to add custom HTML elements within the Story Map Journal side panel. I have been able to confirm this functionality using the Story Map Journal template, but would like to know if this is available in other Story Map templates, specifically the Map Series template.
There is a Story Map that EPA has created that utilizes custom HTML in their application (which is based on the Map Series template), but I haven't been able to figure out how this was done. Is it possible that custom HTML elements in the Map Series template are supported in a hosted Portal release that isn't yet supported in ArcGIS Online?