In my tests these work
app.GetPrivateFolder("foldername"))+"/filename.ext" // user cannot see files
app.GetSpecialFolder("foldername")+"/filename.ext") // user can see files,
foldername should match the type of file
"Pictures" for images, "Movies" for videos, "Music" for sound, "Downloads" for others
This is only for Internal, not an SD card
there are other posts about that (CheckPermission, GetPermission),
Regards. ah