LumaFusion just added full support for external storage in iOS13. You can now edit directly without importing to your iPad storage.
This is huge! Now you don’t need to fill up your internal storage with heavy video files and can work directly from an SSD or HDD just like on a laptop/desktop.
Edit: Looks like this isn’t true after all – I misunderstood the wording in the update. It allows you to browse, preview and trim files and then add them to your project. Not sure if it still copies the entire clip or just the section you trimmed.