You can add a new window only to root of the project or add a new subwindow to any page.
To add a window
1. Right-click on the project object in the Project panel.
2. In the shown context menu select the Add menu item and select Window object
To add a subwindow
By using the context menu:
1. Right-click on the page object in the Project panel.
2. In the shown context menu select the Add menu item, select the Visual object subitem, select the Subwindow object .
By using the Tools panel and the Artboard:
1. Open the page on the Artboard by using the Project panel or the Sheet tabs on the Artboard.
2. Select the icon of the subwindow () in the Tools panel on the Artboard.
3. On the Artboard, draw the subwindow object by dragging with your mouse.
To copy, cut, paste, or delete a window
You can copy, cut, paste, delete a window like any other objects. See Copy, cut, paste, or delete an object. But note, that when you do one of above actions, all child pages of the window will be copied, pasted and deleted too.