coopdawg I can add the volume settings also to the song details view but currently the volume slider in the big player would also modify the stored volume of the song. I'm not sure yet if this would cause any confusion.
Spelolle If you only see a "Stage Traxx 3" folder, than this is the only app you have installed that supports the iOS files app. Where do you have your files stored? Dropbox? That should be visible on the left side under Locations (see screenshot further above). All other file services like iCloud or Google Drive or even Owncloud/Nextcloud are also available under Locations if you have integrated them with the iOS files app.