Вот пример того, как переключить фокус между двумя tkinter windows:
from tkinter import Tk, Button
first = Tk ()
second = Tk ()
first.title ('First Window')
b1 = Button (first, text = 'Goto Second Window')
b1.config (command = second.focus_force)
b1.pack ()
second.title ('Second Window')
b2 = Button (second, text = 'Goto First Window')
b2.config (command = first.focus_force)
b2.pack ()
first.mainloop ()