I pulled down a copy of existing redirects by exporting directly from my WP database. In pHpMyAdmin, click on your database, then on wp_redirection_items. Then click on the browse tab, scroll to the bottom of the page and click export. Choose Excel and viola, bob’s your uncle.
I have done an import with this plugin, and all I used was 2 columns in a CSV file. First column was 404 URL without the domain (eg. /somefile.pdf) and second column was the redirect URL (eg. http://www.yourdomain.com/newfilename.pdf).
Cheers!
This would be great to have an answer to, I just need to export our existing redirects as well. Thank you!