We are developing a Google Slides add-on and we need to add some custom top-level menus. The documentation on https://developers.google.com/apps-script/guides/menus says:
Scripts that are published as add-ons for Google Sheets, Docs, or Forms cannot create top-level custom menus.
But when I installed the publicly available Poll Everywhere for Google Slides add-on, it added the Poll Everywhere menu as a top-level menu for all documents. How could that be possible considering the quote above?