I posted this issue in the Moodle.org forums, and Tim Hunt agrees that I discovered a problem that is a bug.

Apparently, the only way to preview a quiz in Moodle 4.0(dev) is to have “Teacher” role and for the quiz to have a due date in the future.  Mary Cooch’s reply to me does show a “Preview quiz” button, but my experimenting shows that she is likely login in as teacher.  If you have the elevated “manager” role, you do not see the “Preview Quiz” button.  And if you simply want to look at a quiz whose due date has expired, you can’t.

This problem does not exist in Moodle 3.11.6+, nor do I ever recall it in Moodle.  Teachers and Managers have always been able to Preview a quiz.

As a suggestion, I would add the “Preview” menu item under the “More” menu item, like how Moodle 3.x puts “Preview” under the “gear.” Or maybe it should be under the “Quiz” menu item or have its own spot in the menu.

Of course, being able to Preview a quiz is a very essential task.  

I haven’t tried experimenting with all roles and all date conditions.  I am always “manager” in my Moodle, and switched my role to Teacher as I explored what Mary was seeing.