Hello,
All the documentation about programmatic save bar is not working and incorrect here: Forms
Save bar requires an ID but the documentation does not use it. The Save bar currently seems to be the only component from the old ui-* that has not been updated.
Also, I think the data-save-bar works well most of the time, but the current problem is that as soon as you click on it it disappears, making it impossible to show a loading state. It would be nice if the data-save bar would be a bit smarter here.