You can "group" assignments to make it easy to manage. Groups do not affect assignment publishing, grading, etc. Those attributes are set at the assignment or the part level.

Select "New Group" in the "Edit Assignment" page -

Enter the group name and select "Save and Continue"

The group should show up in the list on the left

You can have two options to add an assignment to a group. You can open the group and then dragging an assignment to it

You can also select an assignment and using the "Move to group" selection

You can use the "trash can" symbol next to the group name to delete the group. NOTE: All the assignment in the group will also be deleted if you delete a group.