Hi Brian
You can create your own story map either using the same web map as the one you are looking at, or using a copy of the web map with your own changes in it. So the workflow is find out which web map is used in a story map, then save a copy of that web map, make changes to it, and then deploy a story map using your copy of the web map.
For example in the Austin Shortlist you mention above, if you right-click the map and choose View Source Code (this command name will depend on your web browser because that right-click menu is browser dependent), and then scroll down to the Config section of the file that appears:
/******************************************************
******************** config section ******************
*******************************************************/
var WEBMAP_ID = "91244e9bd6ee422388e90e1474d5ef49";
var BOOKMARKS_ALIAS = "Zoom";
var COLOR_ORDER = "green,red,blue,purple"; // will only use as many colors as you have tabs
var DETAILS_PANEL = false; // specifies whether or not popups have a link to a separate Details panel
you can see the ID of the web map that it uses: 91244e9bd6ee422388e90e1474d5ef49
so you can then open that web map in ArcGIS Online:
http://www.arcgis.com/home/webmap/viewer.html?webmap=91244e9bd6ee422388e90e1474d5ef49
then if you save a copy of the web map you can go ahead and make modifications to it, like editing or deleting layers or features, and adding in your own layers, For example you may want to add your own placesor delete some of the existing ones. You can do this editing in ArcGIS Online. But if you wanted to you could also open the web map inside ArcGIS Desktop and do more advanced edits to the data. For example you could open the web map in ArcMap, save each of the layers as a shapefile, make edits to those shapefiles, and then upload your new shapefiles as .zip files into your web map, which is a standard way of getting new layers into a web map and was how the original Austin Shortlist web map was created. Then you can share your web map and deploy it in your own story map. In the case of the Story Map Shortlist app, you should visit our website and download the app which includes a README that details the format that this app expects for new layers, etc: Shortlist App | Story Maps
