We are working on import masses of questions via question banks. Currently, when you import a QTI file, there is no option on New Quizzes for question bank creation:

Why not? The fact New Quizzes runs as an LTI is probably the reason behind this, which limits a lot of interaction with the core platform.

New Quizzes look nicer, yes, but don't seem to be able to do everything you can do in old quizzes (which work perfectly fine, including on mobile) yet. So for now we are not inclined to recommend them to staff unless they need particular features of new quizzes.