I have never done it in 4.2 or 4.3. Can’t remember in which earlier version I did it, 4.1, or even 4.0. After that I just was importing backup and for almost 3 years I stopped using it at all.
What I can tell for sure is that you have to use the latest updated updated win7 ISO, post-SP1 for sure (Testing Windows and QWT in R4.1 - #61 by GWeck).
Find such an ISO online, it’s not hard. Just type LastWin7
Edit ISO and put qwt there. Install Win7 and prep it properly and check it properly before you install qwt. Make a clone of it.
Install qwt 4.1.6x from withing win7 qube. Test it.
Really don’t know what else to say, except - follow steps strictly and don’t ask yourself (and us) why something isn’t working. Make yourself asking “how this next step will work” instead. My honest opinion is that you are very often “lost in translation” asking why is something happening. Or at least, loosing us to help.
Read the topic posted above and
https://forum.qubes-os.org/t/windows-support-in-qubes/
https://forum.qubes-os.org/t/windows-usb-integration-with-r4-1/