QToolBar can produce an extension menu if there are too many actions to be displayed in the available menu.

That extension button creates a pop-up menu as a default QMenu. By default, QMenus have the toolTipsVisible property set to false. That means that if QActions are added to the QToolBar with tooltips, the tooltips will not be visible when the actions are present in the extension menu. Tooltips for the same actions are present when viewable normally because there is enough space.

It would be handy to have a method to QToolBar to set a property so that the extension pop-up menu was created with toolTipsVisible. Or, perhaps it could be set to true by default, since what is displayed in it are QActions that have their tool tips visible when the space for the QToolBar accommodates them normally.

The QToolbarLayout class is not part of the public API and exists as an internal implementation detail, so subclassing it in order to override the method is not reliable.