If you are logged in to the main file with the credentials used by each of the import files, this may work (I haven't tested)
Have your import script "open" the file first before the import step. It should attempt to open with the current credentials. Then import.
To avoid login dialogs, the source files need to forced open automatically in the background rather than opened by calling the import. If they are open with the same account before the script runs, that might bypass separate logins.
The simplest way to force the source file(s) open is to reference them via relationships (Cartesian joins work) by placing a field from the related source file on a layout which is exposed before import is called during opening.
However, if the source file(s) are remote, this auto-loading of data may be very S-L-O-W, and you would probably be better off handling the manual logins. That is also true if there are multiple source files which would each need their own relationship and field instances.
Thanks, this works. It's a little slow, but works.
Thank you, opening the files first works. And you're right, it's a bit slow; but until FileMaker allows you to import from a closed file or I have time for a different approach, this works for me.