Changes need to be committed. Normally you would do that with a save-button.
Another option would be to commit in an on-change event, though you would need to attach that to each field in your form. Do note that i believe on-change events are not triggered when you navigate away from a form via a menu: this will cause a rollback.
So far i have not seen any intuitive, properly working and maintainable solution in Mendix without something that acts like a save-button. I’ve seen microflow timer being used to commit every x seconds. and warnings to remind the user to save. They all caused confusion and users reporting unexpected data loss.
I am curious is someone can prove me wrong.