3D Labelplacement - more control of vertical placement on multipatches

[OleSeidel1]

Let's say, I have a multipatch polygon representing a window of a building. I move the camare to the same z-Level as the building, looking straight foreware to the fassade of the building. When I turn on Labelling of my windows, those labels are placed on top (above) the window. I need them to be moved down so that they are placed between z-min and z-max of each window polygon so that they look as if they were placed inside those windows and not above. Basically what I need is the capability to apply a (in this case) negative Z-Shift of my label placement.