Suppose one is browsing on Chrome on a regular window, but there is also an (or many) Incognito window(s) open in the background. The user does not want to open them and close the windows one by one, but he or she is also unwilling to close all windows. [Ignore the question of the motivations of the user. This is a purely hypothetical scenario.] In such a case, does there exist a shortcut in Chrome by which he or she may close all Incognito windows without opening and closing them one by one, but no regular windows?
The best way to close all incognito tabs through a keyboard shortcut is to go to the incognito window with Alt+Tab and then Alt+F4.
If you want an extension which closes the current window, and opens another window with an empty new tab, you can use Close All Tabs in order to close a window by clicking the extension's button.
I use an extension to deal with that named "Close Incognito Windows - Keyboard Shortcut".
Then just use alt + w