To disable the pop-up window prompting to save mailing addresses in LastPass on Chrome with the desktop vault extension on Mac, you can adjust the auto-save settings within LastPass. First, open LastPass and go to Settings. Look for the Auto-save section or similar preferences related to form fills or addresses. Disable the option related to saving addresses to prevent the pop-up from appearing when you ship something, ensuring a smoother experience without interruptions, especially when using platforms like gobgautos.