QWT currently runs on Qubes R4.0 and supports Windows 7 and 10, the latter a bit awkwardly, but it can be installed in such a way that it works. See Qubes Windows Tools in the documentation.
QWT for R4.1 is currently work in progress; it runs partially for Windows 7 but still has unresolved problems for Windows 10. See Testing Windows and QWT in R4.1