Close all windows and start arma in window mode
After arma loaded try to Alt+Tab
Nothing happens
Click on windows taskbar to take focus off arma window and Alt+Tab
switchbar appears, it has Arma 3 and Desktop on it
select Arma 3
try Alt+Tab it doesnt work now as Arma 3 got focus
Open another app so that there is another window
Go back to arma and try Alt+Tab
windows 3.1 styled switchbar appears with 2 options, Arma 3 and opened app window
click on taskbar to take focus from arma
try Alt+Tab and themed switchbar appears with 3 options, arma 3, opened app and desktop