When creating a map, why can't I add a shapefile that's already a part of my organization's content? Instead, I must "Add Layer from File" to add the shapefile. I've tried sharing the shapefile with "Everyone" and/or my "Organization" but it does not show in the dialog below.
This screenshot was taken before setting the "Shared" status
The online help ( http://doc.arcgis.com/en/arcgis-online/reference/shapefiles.htm ) states at the very end "you must use the Add button in the map viewer." But does not give additional details as to what data sources can be used.