Create a local analytics configuration, then try to associate a library with it. You'll get the error "The configuration is missing a required field."

Presumably the issue is that the 'associate a new library' form submission is being checked as though it were a "update all the data" form submission.

This doesn't seem to happen in other, similar cases, such as adding a library to a patron authentication service, or adding a collection to a library. But there may be other places I haven't checked where the same problem happens.