How can I add a script to display notifications for webpage updates?

Have you looked into tools like Tampermonkey? It might not be as simple as a custom button or filter, but it could work for your needs. Just a heads up, since you mentioned you're a flight dispatcher, if the program fails due to changes in the website, it could lead to serious issues. If window space is a concern, could getting a second monitor be an option?

You might want to check out using the dev console to add an event handler for the changes you’re monitoring, but keep in mind this would reset every time the page refreshes. Modern browsers block some action that would force a tab to come to the front for user experience and security reasons. For notifications, the Notifications API could be useful. If you're looking for something more automatic, maybe consider writing a web scraping script with Selenium or Playwright that pings the page for updates. By the way, what exactly are you monitoring, and how urgent are those updates?

Unfortunately, you can’t just add code to websites that you don’t own unless you’re developing a browser extension, which might be a bit too advanced for now. It’s a good idea to focus on basics first. Any specific features you’d want to add, or is it just about notifications?