How can I edit Audio Mix on ProRes LOG files stored on an external SSD?

I bought the iPhone 16 Pro to shoot ProRes LOG clips of short music performances. My phone is 128 GB and I store the LOG files on a SanDisk Xtreme Pro 1 TB SSD.

I would like to be able to change the Audio Mix settings for the LOG files, but the Photos app will not import the LOG files for editing (and of course it can't edit them on the SSD).

If I try to import a LOG video into Photos, the import seems to start, but then it quits after 10-15 seconds and returns to the Photos app with no error message. It seems I will not be able to edit Audio Mix at all on LOG files.

The SanDisk SSD works normally to transfer files otherwise in Windows 11. Obviously, it works under iOS 18.1, since the LOG video files do get saved there. So it's definitely not a cable issue.

I noticed that the Devices > Import option in the Photos app appears sometimes only after I push the USB-C cable into the phone and jiggle it a bit; this may actually just be due to a normal delay; I mention it for completeness. As mentioned above, there IS a connection from the phone to the SSD, since the phone is able to save LOG files there normally.