upd

main_window.py

@@ -97,7 +97,6 @@ class MainWindow(QMainWindow, Ui_MainWindow):
         self.import_movie.triggered.connect(self.import_slot)
         self.action_open_project.triggered.connect(self.open_project_slot)
         self.action_refresh_tab.triggered.connect(self.refresh_tab_slot)
-        self.action_export.triggered.connect()
 
         self.action_undo.triggered.connect(self.undo_slot)
         self.action_redo.triggered.connect(self.redo_slot)

main_window.ui

@@ -514,9 +514,9 @@ QPushButton:pressed {
     <addaction name="action_open_project"/>
     <addaction name="separator"/>
     <addaction name="import_movie"/>
+    <addaction name="action_export"/>
     <addaction name="separator"/>
     <addaction name="action_save"/>
-    <addaction name="action_export"/>
    </widget>
    <widget class="QMenu" name="menu_2">
     <property name="title">
@@ -526,6 +526,7 @@ QPushButton:pressed {
     <addaction name="action_redo"/>
     <addaction name="action_view_history"/>
     <addaction name="separator"/>
+    <addaction name="action_insert_aside_from_now"/>
     <addaction name="action_operate"/>
    </widget>
    <widget class="QMenu" name="menu_3">
@@ -536,7 +537,6 @@ QPushButton:pressed {
     <addaction name="actiona_4"/>
     <addaction name="separator"/>
     <addaction name="action_refresh_tab"/>
-    <addaction name="action_insert_aside_from_now"/>
    </widget>
    <addaction name="menu"/>
    <addaction name="menu_2"/>

main_window_ui.py

@@ -308,19 +308,19 @@ class Ui_MainWindow(object):
         self.menu.addAction(self.action_open_project)
         self.menu.addSeparator()
         self.menu.addAction(self.import_movie)
+        self.menu.addAction(self.action_export)
         self.menu.addSeparator()
         self.menu.addAction(self.action_save)
-        self.menu.addAction(self.action_export)
         self.menu_2.addAction(self.action_undo)
         self.menu_2.addAction(self.action_redo)
         self.menu_2.addAction(self.action_view_history)
         self.menu_2.addSeparator()
+        self.menu_2.addAction(self.action_insert_aside_from_now)
         self.menu_2.addAction(self.action_operate)
         self.menu_3.addAction(self.actiona_3)
         self.menu_3.addAction(self.actiona_4)
         self.menu_3.addSeparator()
         self.menu_3.addAction(self.action_refresh_tab)
-        self.menu_3.addAction(self.action_insert_aside_from_now)
         self.menubar.addAction(self.menu.menuAction())
         self.menubar.addAction(self.menu_2.menuAction())
         self.menubar.addAction(self.menu_3.menuAction())