[Tkinter] calling a new window from a tkinter window

[neuroprogrammer]

I'm having trouble navigating nested windows calls with tkinter. The first window builds and executes well, with a window.mainloop() statement at at the end to set up the window polling.

But now, when I use a button to call a function, which in turn, opens up a new window, I end up with a parallel window that does not wait for the return values returned by the second function. In this case the second window is just a simple dropdown menu, with user selected choice, which should be returned to the main function. Everything works, except the code that calls the new window doesn't wait, and then execute subsequent code. I started exploring wait_window(), but don't understand how that might help.