Improve Qt Quick UI Forms Designer

Qt Quick Designer is very buggy, slow, and it doesn't support many features used in real world apps. It freezes Qt Creator and often takes more than 10 seconds to load a simple qml with a rectangle inside it.

I'm sending attached a sample project and a screenshot with several features that are not supported by Qt Quick Designer. These unsupported features are marked as comments in the screenshot.png.

In order to contour these issues, I use internally a modified version of my QtQuickPreview project attached. It would be great if Qt Quick Designer could accomplish something similar. (In case you wish to use it, please remember to register c++ types in frmmainwindow.cpp, line 29).

Qt Creator is great for C++, but I can't find a single person using the Qt Quick Designer. Not even Qt examples use Quick UI Forms!
It has potential, but no love until now