Why can't I dock certain Windows in UE?

I wonder why I can’t dock certain windows to my UE Screens? for instance when you bring up the Hierarchical LOD outliner, it comes as a tab in it’s own movable window. I try to grab that tap abd attach it to the window I already have on my screen but it won’t dock. It insists on being in it’s own floating window. That is pretty annoying since I dont use that window constantly.

Is there a way to force it to dock, or is this a bug or a feature or what?


I was able to get it to dock anywhere in the editor using 4.12 Just keep trying. =)

There seems to be different forms of “top level windows” in UE. You can not dock all tabs into all those windows. I am working with a multi monitor setup by the way and have one top window on each monitor.