Edit Key Photo on Mac, not iPhone
Re: Change the key photo in a live photo on Photos app on a Mac
The above response appears to answer this question, yet when I go into the Editor, I can't find the option to insure I am in "Live" mode, as described. I'm on Photos 3 in High Sierra - what am I missing?
MacBook Pro with Retina display, macOS High Sierra (10.13.6)