Would be really useful if there was the option to add/delete spots to/from an existing polygon (e.g. using option-click or control-click to add and shift-option-click or shift-control-click to delete).
No, what I'm suggesting is much simpler. Let's say I've created a polygon with 15 spots. A couple of hours later I realise I need to adjust it to be 18 spots. At the moment I'd have to delete the polygon and re-do it from scratch. It would be great if I could just add spots to an existing polygon. Hope this clarifies.