@Frances Proctor and @pruus thanks so much for your help. Frances your method was what I had in mind because it remains editable. I've been playing around with it and it's def what I had in mind. The only issue I have so far is that, when I need it, I have struggled to get an (approximately) even distribution between inner and outer curve, as in example below.
Using the corner tool though, it's a piece of cake, although as you mentioned it's no longer editable.
Pruus your method was effectively what I was doing, although I didn't realize you could edit the outer and inners simultaneously. I was laboriously shift clicking the the inner nodes, rounding the corners, then doing same for outers. Now so much quicker!
I guess the most efficient way to proceed would be to use the star Smart Shape, but when necessary make different configurations with the corner tool and save them to a new category (seals, badges, whatever) in Assets.