QT Designer problem.
There is a default toolbar in my form, when I drag a push button on it. It says no and can't add to it.
The tool bar is a drop target for actions not widgets. Corresponding QToolButtons are generated for actions on the tool bar.
"Creating Main Windows in Qt Designer: Adding and Removing Toolbar Buttons":http://qt-project.org/doc/qt-5.0/qtdesigner/designer-creating-mainwindows.html#adding-and-removing-toolbar-buttons
If you really want to put a standard widget on the tool bar you will have to do it in code with QToolBar::addWidget()