QUESTION:

Why do the windows (or child objects) inside some walls not nudge in certain directions ?

ANSWER:

When you insert a window in a wall, the window knows that all its nodes must be on the same plane as its parent and completely within the boundary. In turn, the wall then knows to subtract the surface areas of any windows inserted within it and to let light pass through, etc. When you nudge a window, it will try to remain within the plane of the parent. In some directions it simply can't do that so it will not appear to move at all. If you are nudging in the X direction and it doesn't move, simply try the Y direction instead. When nudging, you can move windows outside their parents (in which case they will turn red) as it reasons that you must know what you are doing. When dragging a child object with the mouse however, all nodes will try to remain inside the parent as it reasons that, if you had wanted to drag it away from the parent object, you would have unlinked it first.