MichaelSchultzPhotography

Hi guys I did a workshop recently and was interested to see that when the photographer edited in photoshop from Lightroom the edited file came back to Lightroom and automatically stacked. I can't seem to get this to work, I have gone into "External Editing" and ticked "stack with original" but it doesn't seem to stack. I have to manually do it, which is a pain. Ideas on how to get this to work? Cheers Michael