PublishPress Future Pro supports imports from external data sources. You can import posts and automatically create Future Actions associated with those posts.
The best approach is to use the Metadata Scheduling feature. This post explains the technical details of PublishPress Future, but it's not currently possible to import directly to the ppfuture_actions_args table.
If you're using a plugin such as WP All Import, you can match up the import tables with the fields you have selected in the Metadata Scheduling feature.
