You can make the Process Portal switch the page that a user can see.
You can code a widget to make Process Portal switch the page that the user can see. That is, your widget behaves as if there was a Page Navigator widget with a Switch Page action wired to it. The page can be in the current space or in a different space. If the page is in the current space, the behavior is like the user clicking a different page tab in the space. If the page is in a different space, the behavior is like the user selecting to go to another space and then selecting which page to open. However, unlike using a Page Navigator widget, you cannot define a target event to pass data to the switched page.