My first idea would be to use a list view with a listen to widget dataview to get the functionality and css to make the whole thing look like tabs.
Tab Extension (Dynamic tab names, Buttons), a widget in the AppStore should cover you in setting up the names of users as the tab titles? I haven't used the widget myself. But says to be compatible with Mendix 6.0.1 and up, so I guess it should work with 6.9.
But from an interaction design perspective this seems to me like a horrible solution for larger groups of users.
Otherwise, if this widget doesn't cover your needs. You can always use a listview with all the users in it, and make a listen to widget show the content of the "tab"