Yeah, none of us uses Windows...
I hoped someone of the real Windows users would participate.
@kugel- thanks for a concrete suggestion. For me, B00merang-Project/Windows-10 has the same problems as @techee mentioned in https://github.com/geany/geany/issues/3063#issuecomment-1008428973. So, for me it would also be better than the current Adwaita theme but not good.
Some random alternatives, just in case any of them reaches more consensus: - https://github.com/sinner59/windows10-theme - https://github.com/sinner59/windows10-flat-theme - https://github.com/zayronxio/windows11-GTKtheme