I see an 'add' button on the page for Scotland, or Aberdeenshire or whatever, but only if I go to it directly via search, not if I go through the "Sites" menu. Is that the same for you?
Ah … that hadn't occurred to me. The new 'Sites' view doesn't actually show the content for the region you're looking at, just the sites within it. I'll have a think about how to add content/sites to the selected region via this method as well as how to present any content that exists in that view. 👍