Pinning questions on a test will keep them in the pinned location and order, even when other questions are shuffled. To pin a question on a test, click the question number so the entire question is selected. Then click the pin icon on the toolbar. Repeat for other questions as desired.

There is another option to group two or more questions together by linking them to a shared Instruction. TestGen Help gives directions for how to set up an Instruction and link it to two or more questions when editing a testbank (not a test). Note that when questions are linked to an Instruction, they can still shuffle within the group unless, when placed on a test, questions are sorted in Testbank Order.