Some time ago, IDLE's main menu item 'Windows' was changed to 'Window'.  The latter seems to be pretty standard for a list of open windows.  Issue #33906 changed the implementation module name accordingly, from 'windows' to 'window'.  This issue is about changing the 'windows' key in mainmenu.menudef to 'window'. All other keys are the lower case version of the uppercase menu item.

editor subscripts derived menudict with ['windows'] and menu_specs, which maps menudef keys to menu names, includes ('windows': '_Window'). pyshell also has menu_specs

Function and pseudoevent names that include 'windows'should be left alone.

Besides the automated tests passing, the manual test will be that 'Window' works properly in all of Shell, editor window, and output window, as each is added.