Add corner widget to maya main menu bar.

add_corner_widget_to_maya_main_menu.py

from Qt import QtWidgets


def getMayaMainWindow():
    # type: () -> QtWidgets.QWidget

    for obj in QtWidgets.qApp.topLevelWidgets():
        if obj.objectName() == 'MayaWindow':
            return obj
    else:
        raise Exception("Maya main window not found")


def injectWidgetToMainMenuCorner(myWidget):
    # type: (QtWidgets.QWidget) -> None

    for kid in getMayaMainWindow().children():
        if isinstance(kid, QtWidgets.QMenuBar):
            menuBar = kid
            break
    else:
        raise Exception("menuBar not found")

    corner = menuBar.cornerWidget()

    layout = corner.layout()
    layout.addWidget(myWidget)
    layout.update()