I see that Duplicate Label Class was added in 2.8, but only in the List by Labeling view. I didn't know it was there until I searched for it on here and watched the Ideas in 2.8 video - I rarely use this view, and it can be a hassle to navigate to if you're in layout view or need the contents pane for something else. I think it would be more intuitive to include the duplicate option from the hamburger menu in the label class pane - where you're already working on your label options, and likely to have open when you need to duplicate. It might also make sense on the Labeling tab somewhere - in the label class group perhaps. Redundancy isn't always bad.