How to prevent Mac OS X El Capitan from automatically switching desktop when new application is launched
There is no way to change this behavior. The reason is because your full screen application is contained in a separate virtual desktop, leaving the "default desktop" available for any other apps to run (like the case of efficiency on multiple screens). OS X &amp; macOS work like that. Every aspect of the OS was designed in a way to be "clutter free", so a window on top of a window is a big no no for apple, and will be avoided if possible.