Any news? I have the same issue on a UHD screen (3840x2160). InSync is ridiculously small.
May I kindly suggest to follow suit in existing desktop applications rather than to create yet another scaling setting? I have configured my KDE desktop to use a scaling factor of 1.5 and have increased the system DPI to 168 so that I get reasonable sizes in applications that use these settings (which actually most applications do). Adding separate DPI settings for each application doesn’t make it easier to use.