In a fit of energy I re-arranged the layout of the studio slightly. Keyboard against the wall; desk facing the window. The custom-designed-and-built studio furniture unit is unchanged positionally except for sliding a foot to the right.
Reflections from the window are reduced. Mission accomplished. On the other hand, when I'm working at home in day-job-mode I now have my back to the door which is not great. On the gripping hand, I can look out the window as I daydream work.