I searched for this and didn't find anything specific.
Would like the ability to add photos from files or cloud storage on mobile. When you want to add a photo, the mobile device gives you the option for your camera or gallery. It also links to Google Photos. Would like to be able to open other cloud storage or device files to add photos. I personally use OneDrive to backup/sync my photos. I cannot access my OneDrive photo file from the camera options in the mobile app. This does work on Windows version.