Hello - this feature is now available. You can read more about it here: https://flow.microsoft.com/blog/support-for-sharepoint-document-library-properties/
This feature has been completed, you can read about it here: https://flow.microsoft.com/blog/planner-triggers-connector-improvements/
There is now a trigger in SharePoint that will fire for any file created in a document library. You can read more about that here: https://docs.microsoft.com/en-us/connectors/sharepointonline/#when-a-file-is-created-or-modified--pr... . This includes subfolders in that document library.
We are working on enhancing our approval functionalities.