Please try closing the control panel (either by right-clicking on it, or via the View menu), then re-opening it. It should then appear in its fully-default position (whereas in other cases it would remember its last position whenever an organ loads). Its default position will be relative to the top-left of the primary Hauptwerk window (the one with the main menu bar).
Does its left-hand 'handle bar' then appear on one of your monitors?
chr.schmitz wrote:Interestingly the "missing" part of the panel does not show up on the left monitor (something I would expect).
Perhaps you have a third monitor somewhere, and the left-hand portion is currently visible on that? The underlying multi-platform library that Hauptwerk uses (Qt) should always ensure that the windows get restored/positioned at a valid coordinate within your operating system's configured desktop area. How do you have your monitors laid out within the operating system?
chr.schmitz wrote:BTW: The Master couplers control panel seems to be wider than 1080 pixel. It will never fit completely on a portrait screen, even if the resolution HD
It's actually 1059 pixels wide, so it should fit on your screen (just!).