It worked for me! Thanks a lot. In my case it was:
+ActiveClassRedirects=(OldClassName="/Script/RuntimeTransformer.ScaleGizmo",NewClassName="/Script/RotateObjects.ScaleGizmo")
RuntimeTransformer was a plugin and I moved the class into my main project called RotateObjects.
Also after you save the object from the editor, you can then remove the line from DefaultEngine.ini