Tkinter Menu makes no Tab [Windows only]
I think you are out of luck. Menus in Tkinter are native, so you're at the mercy of Microsoft.
If you're trying to provide a string that represents an accelerator, use the accelerator attribute instead of faking it with a tab in the label.
menu1.add_command(label='Informationen', command = info, accelerator="F5")menu1.add_command(label='Beenden', command = ende, accelerator="esc")