On windows only by stretching the window over both windows and undocking your tabs and resizing.
Personally I use my 2nd screen for browser, e-mail, PDF documents and undockable palettes (profile manager, SEO, etc). Back starts to hurt if I work on both screens.
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
Windows 10 Pro
Adobe Design Premium CS5