Song Surgeon 6 does allow you to access files stored on Apples iCloud service.    The iCloud drive is labeled as "com-apple-CloudDocs"  as shown below.  This name is not something we can control, it is assigned by  your OS.   If you browse and select this folder from within Song Surgeon you will be able to access any of the audio files you may have saved to the Cloud and open them in Song Surgeon.