window header and sill

In the CONNECT Edition, there are _Header & _Sill items under the Window placement. Shouldn't these be dependent on the host window? If I place these and select the window as a host, if I move or change the size of the window, these do not change? They don't seem to have any intuitive nature to them, like the height location should be set relative to the window for example.

On a related topic, is there any way to place interior or exterior trim on a window? Are these the only options?