From Audacity Manual
Minimizes the front project window into the Dock. Same as clicking the yellow minimize button at the upper left of the window.
If the front window does not fill the entire screen (except for the Dock), zooms the window to full screen. If the window was previously zoomed to full screen with this command, clicking it again will zoom the window back to its previous state. Same as clicking the green zoom button at the upper left of the window.
Bring All to Front
If any windows are hidden they will be shown. Does not bring windows out of the Dock.
List of open windows
Contains an item for each open project. Selecting a project window from this menu will bring it to the front and make it active, retrieving it from the Dock if needed. Any project that has never been saved will just be called "Audacity". The active project window will have a check beside it. A project window in the Dock will have a diamond beside it.