is there a sure and simple way to test, via script or ...., an FM file to determine if it is setup for External Storage. I am am aware that we can look to the contents of a container, but is there another way ?
Why wouldn't you look at the contents to determine this? There's text that can be extracted from the container that can tell you this after all.
While the file can be set to have external container paths, external storage is set at the field level.
You would need to check the container with GetContainerAttribute to see for sure on each container as some may be internal and some external.
My only other thought would be to use a plugin to run a system script to check the folder size of the default external storage folder, but that is not super reliable give the folders can be managed.
Retrieving data ...