add_tab.py

from PyQt4 import QtGui,QtCore
#from PySide import QtGui,QtCore
import FreeCAD

def getMainWindow():
    "returns the main window"
    # using QtGui.qApp.activeWindow() isn't very reliable because if another
    # widget than the mainwindow is active (e.g. a dialog) the wrong widget is
    # returned
    toplevel = QtGui.qApp.topLevelWidgets()
    for i in toplevel:
        if i.metaObject().className() == "Gui::MainWindow":
            return i
    raise Exception("No main window found")



def getComboView(mw):
    dw=mw.findChildren(QtGui.QDockWidget)
    for i in dw:
        if str(i.objectName()) == "Combo View":
            return i.findChild(QtGui.QTabWidget)
    raise Exception("No tab widget found")

class test(object):
    def setupUi(self,object):
        self.pushButton = QtGui.QPushButton(object)
        self.pushButton.setText("The Button")
        self.pushButton.show()

        QtCore.QObject.connect(self.pushButton, QtCore.SIGNAL("clicked()"), self.make_it_happen)

    def make_it_happen(self):
        FreeCAD.Console.PrintMessage('You pressed the button!\n')

    def kill_the_button(self):
        self.pushButton.hide()

mw = getMainWindow()
tab = getComboView(getMainWindow())
tab2 = QtGui.QTabWidget(parent = mw)
tab.addTab(tab2,"A Special Tab")
panel = test()
panel.setupUi(tab2)



#tab.removeTab(2) #remove tab2