Hi Molly,
Yeah, that story I referenced has been unshared.
I just wanted to check that you know that the Side Accordion layout is one of the layout options in the Story Map Series app template. Click here for a visual guide to the Map Series layouts.
Here's a Story Map Series using the Tabbed layout in which a Story Map Series using the Side Accordion layout has been embedded into one of the tabs ("Transit Tools"). The other tabs embed a Story Map Cascade, and Story Map Journals!:
http://urbanobservatory.maps.arcgis.com/apps/MapSeries/index.html?appid=1c32233ab04241a08f6bbc80f668...
In general, we tend to suggest keeping story maps simple and not embedding story maps inside story maps, but it is a technique that is used a lot especially for more in-depth stories where authors like the extra storytelling bandwidth they can get. For example, this story by George Washington's Mount Vernon is a Story Map Journal with two Side Accordion Map Series and a Swipe story embedded in it:
http://mountvernon.maps.arcgis.com/apps/MapJournal/index.html?appid=3ca8ba42c90a41d39df64b9cd4f25f58
Embedding a big variety of different apps inside a story map, or multiple levels of embedding may be a bit disorienting for casual readers and may be a bit harder to use on mobile devices (because readers will see the mobile UI of the embedded app inside the mobile UI of the host app), but that depends on what is being embedded.
We don't see a lot of Story Map Series stories embedded inside Story Map Series stories. The most common pattern is to embed Story Map Swipe/Spyglass stories into Map Series or Map Journal, in order to provide a swipeable map as part of a larger story. Another pattern that we see a lot is Story Map Journals embedded into Story Map Series, which works especially nicely if each of your embedded Map Journals has the same look and feel. For example see:
https://arcgis-content.maps.arcgis.com/apps/MapSeries/index.html?appid=fbf644cbbba441c7bd9b1a00d03c8...
https://icfgeospatial.maps.arcgis.com/apps/MapSeries/index.html?appid=58f90c5a5b5f4f94aaff93211c45e4...
Some authors are getting nice results embedding Story Map Cascade stories inside tabbed Story Map Series, often as a way to present a set of Cascades in one interactive flow. For example see:
https://icfgeospatial.maps.arcgis.com/apps/MapSeries/index.html
http://eastduncouncil.maps.arcgis.com/apps/MapSeries/index.html?appid=51657d2fb4694f74bfec5a42e32a92...
Hope that helps
Rupert