How to Parallel functions to change the menu and or the buffer?

How to Parallel (Run more then 1 function simultaneously parallel to the application) functions to change the menu and or the buffer in a fullscreen app ? And is it possible to change layouts dynamically ?

I have tryed this:

def run():
    t1 = threading.Thread(target=application.run())
    t2 = threading.Thread(target=testprt())
    t1.daemon = True
    t2.daemon = True
    t1.start()
    t2.start()
#    application.run()

if __name__ == '__main__':
    run()

The testprt()

def testprt():
    while True:
        up_r_buffer.text = "1\n"
        time.sleep(1)

FullCode:
Here

Start with the inline Python example and the linked Pastebin code, then inspect how the application, menu, and buffer are used in the reported fullscreen scenario. A useful outcome would require a scoped, reproducible question and a decided answer or documentation change covering parallel execution and dynamic layouts.