[rsgrn]

I did this recently too. You might want to review the language changes from C++11 and C++17.

You could try writing a raytracer, or physics sim, or small tools that would have been difficult/annoying previously (like dealing with JSON). You could revisit writing win32 apps. The WebView2 lib (which is Edge) is self contained-ish and interesting to learn with (lots of async).