2. There is a filter 'not in an album' which would do what you want. The library view is the equivalent of "All Mail" in Gmail. In newer versions, this is a distinct view - they are moving albums, automatically generated collections and search to be a primary interface.
3. Both WebKit and Mozilla have said they consider the local access variant of that API to be harmful, since they do not have an adequately prominent way to surface and manage that you've given a web application permanent access to sensitive directories and files, potentially in the background via service workers. Both do support the origin private filesystem variant. Are there productivity apps direct filesystem access would be useful for other than IDEs?
