Do you mean you want a page as the top level menu item, then categories as children of them?
In which case I think the best way to do that via the PixoPoint Menu plugin would be to use the "Categories" menu item and choose the "single dropdown" option to make them all appear in a single dropdown, then set the URL for the top level link as the URL for the page you want, you can also change the title for it this way too.
I understand your suggestion and it works, but in a multilingual site, categories are changed to the other language, but the url and the title of the top level link can’t be translated.