This is present, but accessed a slightly different way than in Classic Quizzes.
In New Quizzes, it will require that you have an Item Bank set up with questions already in the bank first. Then, when adding a question in Build mode, you will be prompted to select a question type. In the upper right corner of that popup is an icon that looks similar to a file folder. Click on that to pull up a menu to select an item bank. At the top of the bank, select the button that says +All/Random. This will load a spot into your quiz. Close the Item Bank side panel and click on that spot that was added. You will see an option to choose all questions or a random set of questions. If you choose random, it will expand and let you choose how many questions to pull from the bank and the point value.
Do this procedure for whichever item banks you want to use. When you assign the quiz to students, it will randomly pull questions from the bank(s) you have used in your quiz for each student. The more questions in your item bank, the more random each quiz becomes.