Hi Rob,
I have mentioned this to Sinar and they recognise it is missing from CaptureShop, but I can't remember if they told me if a solution is planned or if they consider using eXposure the workaround for this. Imho it seems the future of Sinar is with tethered-only backs, which have no screen, so maybe a shading mode in CaptureShop is not a priority. The eMotion backs and eXposure software were originally Jenoptik products, rebadged as Sinar, and now that relationship is over I imagine Sinar will be sticking to what they know and do so well, which is specialising in high end studio capture hardware.
Ben