> Apparently they've integrated the open file dialog with their access control, so any such dialog will automatically permit the app to access the target file/folder. The pop-ups only appear when an app wants to access specific folders in the background. This is brilliant and would stop e.g. malware which encrypts documents or nosy apps in their tracks!

This pattern is called "powerbox", an idea from object capability security. I'm sure there are plenty of other usability improvements in there if you study those ideas (more so the more important security is to your application). Applying it to the web is getting easier with Mark Miller's JS standardisation work and (also his) https://agoric.com/ and https://ocapjs.org/