Exported to an iPad a manuscript containing 20+ chapters (files). The files exported ok, but they did not export in order. Is there a key to get them exported in the order they are in the manuscript?

Why are you exporting at all? If you have Scrivener on the iPad, you can just transfer the entire project.
scrivener.tenderapp.com/help/kb … g-with-ios


Assuming you aren’t using the iOS version of Scrivener, have a look at §14.3, Synchronised Folders in the user manual PDF. It offers two-way syncing using regular text files, and has an option for numbering them so that they stay in the right order. All you need on the iPad side is something that can edit files, preferably via some cloud interface, but it’s not even a necessity the way this system is designed to work.