Access to Final Cut Pro files through extension

Hi,

I am developing a Final Cut Pro workflow extension. I would like to upload a Final Cut Pro video with the extension. As far as I understand both the macOS app and the extension are sandboxed and the user doesn't have a direct access to the Final Cut Pro folders. Here there is a described way to receive media through a custom share destination. So far I have been able to parse the XML describing the video after dragging the video from FCP and dropping it in the extension. I have the URL of the video but no access to it - permissions denied.

Can I programmatically acquire access to the folder/ file in question? Or have the user allow access at the beginning and use it later? Or should I use custom shared destination for that purpose?

Thank you in advance!