On Mac OS X, QActions that have a text that starts with "setup" do not appear in menus of a QMainWindow, regardless of capitalization.
E.g.: if the QAction's text is "setup", 'Setup", "sEtUp", or "Setup whatever", the action does not appear in the menu to which it is added.
If the text is "Whatever setup", or "Zetup", it does appear.

This is easily reproducable with a small code sample (attached), but also in Qt Designer (the menu items starting with "setup" don't show up in the QMainWindow's preview).