This makes little sense. Portfolio pages seem to be the same kind of object whichever portfolio they are in.
It looks like a low hanging fruit implementing this and a huge time saver for the users.
After deciding to split my work into a couple categories I am now tasked with redoing multiple pages from scratch just because there can't be a simple option in the "..." menu or settings for whatever reason.
It's one, two APIs, few DB calls and minimal UI changes. Maybe you'll have to make a modal and filtering down to Portfolio pages as options, oh wow)