Items can be saved via menu action and when exiting application with unclean undo stack.

mainwindow.h

@@ -54,6 +54,9 @@ class MainWindow : public QMainWindow {
   void onCleanStateChanged(bool clean);
   void onShowUndoViewToggled(bool checked);
 
+  /// 'File' slots
+  void saveItems();
+
  private:
   Ui::MainWindow* ui;