All written in Python, recently moved to Qt5 and PySide2, runs on Windows and when I figure out packaging for Linux (probably AppImage) will release it for Linux as well.
I believe there are Qt bindings for other languages too.
So you're not stuck with C++ :)
I use Qt Designer for the layout. I never could get the hang of the Horizontal & Vertical spacers or the Layout Managers in Qt, so it's a static layout.
There are quite a few "pages" in the application which appear or disappear when required. Those are all QWidgets which have their own static layout.
The doughnut chart showing materials available on a planet is a dynamically created web page shown via a QtWebView widget.
There's an Overlay Widget which is basically a QWidget with transparency, with the main window being hidden then called up via a global hotkey - I use Python ctypes to enable the global hotkey, calling the Windows API to enable that functionality.
And the underlying databases used are sqlite3 via SQLAlchemy.
It all works very nicely.
