You can move or reorder assignments after you've created them. You can manually drag and drop the assignment, or you can use the Move To option, which is also accessible for keyboard users. You can also move all assignments in an assignment group to another assignment group.

Note: If you are using Multiple Grading Periods, you cannot move assignments and quizzes that are part of a closed grading period to another assignment group. However, you can move open assignments and quizzes to another assignment group.