In Microsoft Project, there is a function located under the Windows menu called Arrange All. If you have two projects open, clicking Arrange All displays one project stacked on top of the other project.
Many people, however, find it more convenient to work with multiple projects by displaying the projects side by side. The Arrange Projects Side-by-Side Widget automatically arranges each of your open projects side-by-side at the click of a button.
Microsoft Project’s Arrange All button arranges projects vertically.
Project Widgets’ Arrange Projects Side-by-Side Widget arranges projects in a more user-friendly view.
With just a single click, you can re-arrange the projects on your screen so that they are adjacent to each other.