Edit Maya Outliner MenuBar

editMayaOutlinerMenuBar.py

from maya import OpenMayaUi as omui
from maya import cmds, mel
import sip

from PyQt5 import QtCore, QtWidgets, QtGui

## Maya pointer to outliner widget
outliner_pointer = omui.MQtUtil.findControl('Outliner')

## Convert outliner maya pointer to QWidget
outliner_widget = sip.wrapinstance(long(outliner_pointer), QtWidgets.QWidget)

## Get ToggledOutlinerLayout
toggle_outliner = outliner_widget.children()[1]

## Get Outliner Panel widget
outliner_panel = toggle_outliner.children()[1]

## Get outliner menu bar
menu_bar = outliner_panel.children()[-1]

## Get outliner menu items
menu_list = menu_bar.children()[1:]

## Create set menu
set_menu = QtWidgets.QMenu('New Thing', menu_bar)

## Change index order of menus
menu_list.insert(2, set_menu)

## Clear menu bar
menu_bar.clear()

## Re-add menus to menu bar
for each in menu_list:
	menu_bar.addMenu(each)