Switch Chrome page with full sze image to Full Screen Mode

A script I am working on generates a Python page of thumbnails in 7 columns. By left clicking on any thumbnail I can generate a fullsize image of it in Chrome. What I want to do is have a button which I can click on to switch the Chrome page to Full Screen Mode. Clicking on the button again would switch the Full Screen mode back to just viewing the image full size again in Chrome. My problem is that I can’t generate the full size image in Full Screen Mode. I always end up with the page of thumbnails switched to Full Screen Mode. I’ve abandoned trying to use pyautogui and pygetwindow as gw as they always mess up the button size and reduce my full page of thumbnails to smaller thumbnails whch take up only 2/3rds of the page.
I know I can generate Full Screen Mode by the use of Fn+F11 but I want to use a button instead. Grateful if anyone can suggest how I can achieve this. Here is the snippet.

    def toggle_fullscreen(self, event=None):
        self.is_fullscreen = not self.is_fullscreen
        self.root.attributes("-fullscreen", self.is_fullscreen)
    
        # Minimize or hide button navigation window during fullscreen
        if self.is_fullscreen and self.nav_window:
            self.nav_window.withdraw()  # Hides the nav window
        elif self.nav_window:
            self.nav_window.deiconify()  # Restores the nav window when exiting fullscreen

    def end_fullscreen(self, event=None):
        self.is_fullscreen = False
        self.root.attributes("-fullscreen", False)