Unfortunately not, there is no area behind a login. I would therefore have to get the Matomo VisitorID somehow. Apparently this is stored normally in the cookie, but Matomo also recognizes the user by fingerprinting. So it should be technically possible that a JavaScript call by the user is answered by the Matomo backend with the VisitorID, completely without cookie. Unfortunately I have no idea how.
At least in Europe, the abandonment of cookies is gaining ground very quickly right now, so such a function makes sense from my point of view.