I have created a
QDialog based app using Qt Creator and all is well other than the dialog has no minimize button. How can I add one? Is there a property in the designer that I can set?
You can't add the minimize button yourself as it is handled by the window manager. You can tell the window manager how your dialog should be handled using Window Manager hints. This is done using the windowFlags property of your widget. There's also an example demonstrating this.
setWindowFlags(windowFlags() | Qt::WindowMinimizeButtonHint);