The GUI is working in both W7 and W10, but restricted to a few screen resolutions, just as desribed earlier in Testing Windows and QWT in R4.1: For Windows 7, screen resolution is restricted to 1920 x 1200 (my physical screen size) and 800 x 600. For Windows 10, the supported resolutions are 1920 x 1080 (HD), 1024 x 768 and 800 x 600. The GUI behaved quite normally in these resolutions - no glitches or so. W7 could be changed to seamless mode, which worked, too, but did not show the Start button.
For both systems, I used copies of the templates used in January which were prepared for QWT installation (testsigning set), but had no previous installation of QWT. In both, I installed QWT with the default configuration, i.e. the basic Xen drivers, but no Xen Disk or Network drivers. For W10, I tried with those two drivers enabled, but the installation stuck and had to be aborted.