Render on existing window

Currently, when we launch UE application, a window is created and the entire content of the window is rendered. What I would like to request for the existing window to be designated as render window (and therefore, not needing to create a new window). Probably we can supply the window handle (HWND in MS Windows) during the creation, and this window will be used for rendering purposes.

This is extremely useful for editor like application where we want 3d content to be rendered only on certain child window.