Master Pages

Yes, it's a Runway feature.

What about at template level? I've set new subpages use a specific Master Page but the regions on the subpage still allow a choice of templates.

In the docs I can see it says "The setting New Pages Should Reference this Master Page, means that when new pages are created they will use the Master Page as a reference and any future changes you make to the Master Page design will be reflected in pages created from it – this is the most usual choice."

I'm struggling to find that "New Pages Should" setting - any pointers? Thanks!