Glad you like it! Good question about how did I find that variable. It's been over a year and I tried to trace the history of that discovery and I cannot fully recall. This page:
https://doc.qt.io/qt-5/qtquickcontrols2-material.html ... mentions the environment variables. I think it had been a lucky coincidence. I had been racking my brain trying to figure out how I would toggle these rectangles without a rebuild, and then I was working with the Material Style feature in QML and I think that when I came across the table on that page labeled "Environment Variables" it just clicked and I realize it could be the answer I was looking for.