Is it possible to disable the ""Leave Site?"" alert on form?

Using Javascript you can do this. Look up the various ways to implement it into your app and pick the one that is best for you. If you want to use JavaScript everywhere in the app then look into the iol technique.

https://community.quickbase.com/quickbase/topics/javascript-for-a-formula-url-to-reload-the-browser

The answer to your question is a bit further down in that topic and involves window.onbeforeunload = null; . The formula there does something else but there is a lot of good info here for your issue I think.

I just tested using the above command and it did prevent the box from popping up when closing a form.