You can work with several maps at once. Using the Window menu commands you can arrange the Map Editor screen so that the maps are easy to see:
The Tile command resizes and arranges the Map Editing windows side by side.
The Cascade command resizes and layers the Map Editing windows so that each title bar is visible.
The Arrange Icons command arranges all minimised Map Editing windows into rows in the bottom left corner of the Map Editor screen.
The Next command moves the Map Editing window at the top of the viewing order to the bottom, activating the window that was immediately below it.
The Previous command moves the Map Editing window at the bottom of the viewing order to the top and activates that window.
The Window menu also allows you to open a map being edited by clicking on its name in the menu.