Cloud CMS supports two options here:
- Multipart HTTP POST. You can post multiple files for upload that all goes as part of the same HTTP request. The general "upload files" option in our UI actually does this (you can drag/drop multiple files into it and they'll all go at the same time) or you can call this kind of this manually. It's standard HTTP multipart and so this works natively for anything you upload.
- Import an archive. We provide a command-line tool that you can use to take documents and package them up into an archive. The archive can then be upload and imported all at once. This is a lot trickier to set up but gives you a way to bundle your assets together and import them all at once on the same changeset (single transaction).