FWIW I really appreciate the design of Gtk.jl and would like to use it.
But my problem with Gtk is that it really is very rough on Windows (and also Mac), unless I have missed something. And this is made even worse on very high resolution displays. Qt on the other hand does much better on both platforms. This is not a minor issue, ugly GUIs really do put people off in a slightly irrational way (the functionality might be perfect).
If Qt with its C++ baggage is too much, then maybe https://github.com/andlabs/libui and https://github.com/joa-quim/Libui.jl might be a nice solution; but I haven’t looked into it much yet.
The simplest solution would be that I am just ignorant and have missed the trick to make Gtk useable on windows.