Office button - Word Options - Advanced tab, Display section. If Show all
windows in the Taskbar is un-ticked, then you'll have a 2nd X below the main
X. The 2nd X can be used to close only the displayed window.
Note, if a document is displayed in two or more windows (e.g., as
mydoc.doc2:1 and mydoc.docx:2), then this 2nd X will close just the current
window on the document, not all windows on that document, same as Ctrl+W and
Ctrl+F4. To close all windows on the current file, choose Office - Close,
which executes the FileClose command.
Note that Word has a number of related "close" commands:
DocClose - Closes just the current window (Ctrl+W and Ctrl+F4)
FileClose - Closes [all windows/view of] the current file (no default key
assignment)
FileCloseOrExit - Action depends on "Show all windows in the Taskbar"
setting. If on, Alt+F4 closes just the current window. If turned off, then
Alt+F4 closes Word, prompting to save changes in each open document.
FileExit - Closes Word (no default key assignment)
FileCloseAll - Closes all documents, but leaves Word open (no default key
assignment)
FileCloseOrCloseAll - like the other OR command, action depends on "Show all
windows in the Taskbar" setting. If turned on, this command closes the
current document, but leaves the window open. If turned off, it performs a
FileCloseAll. (no default key assignment)