In Firefox, you save a new statement, you can still click on "add qualifier" which is normally clickable only when you edit a whole statement.
I can confirm this. You can even add the qualifier, but there's no option to save it. No save button and pressing enter doesn't do anything. When you click edit on the statement you get the possibility to save the qualifier without the need of re-adding the qualifier, the information is still present. But when you can add a qualifier, you expect to be able to save it as well.