@penguin42 OK, so I've hit the "Command" key, typed "Extensions" and a thing shows up.
I seem to have paired the phone and the laptop, and I can transfer one file at a time using the interface on the phone.
But I can't select a collection of files and transfer them all, and it's completely opaque as to how I might see the phone as a filesystem from the laptop.
I going to have to give up for the night. It's late, and I have work tomorrow.
If I can, I'll document carefully a process that I go through that confuses me so people can tell me where and why I'm being stupid.
But for now, I'm going to have to sign off.
Thank you ...