The function to open up a second comp viewer (with a sub comp) to view two comps next to each other at the same time, SEEMS TO BE MISSING IN AE CC 14.
or does anyone know where I might find it.
It used to be in the comp pop-up menue at the upper left corner of the comp window. but it´s not there anymore....
It's not missing. Click the blue text in the Composition panel tab to open the menu that you're referring to.