I did use Qt Quick and I've been having such a great experience (as someone that used to program GUI imperatively via Qt C++ or using other framework like React/React Native) in my opinion, Qt C++ and Qt Quick is the best combo for a GUI framework. You get the performance of C++ and the simplicity, fluid animations, reactivity of QML, etc... My block editor is build in such a way that the models are in C++ and the views are in QML. This separation of logic and presentation works really well. I'll probably wrote a blog post about it.