If you are working with a Referenced Library, but when you use a plugin or external editor the new version of your photo shows up as Managed, it’s probably a permissions issue on the hard drive containing your master photos.

If Aperture doesn’t have permission to create new files on that drive, then it can’t do it, and will automatically create them in the Aperture library (managed) instead.

To fix this, select your hard drive in the Finder and choose File > Get Info.

At the bottom, toggle open Sharing & Permissions if it isn’t already.

Enable Ignore ownership on this volume. You will probably have to unlock it first; tap the lock icon and enter your admin password.

Now, Aperture should add newly generated, externally edited files next to the original master (referenced) instead of in the Aperture library itself (managed).