Geany (and GTK users in general): if you want to disable caret/cursor blinking and force a dark theme, there are corresponding settings in your GTK settings.ini, e.g.
gtk-cursor-blink=false
gtk-application-prefer-dark-theme=true
There are many more:
GTK 3: https://docs.gtk.org/gtk3/class.Settings.html#properties
GTK 4: https://docs.gtk.org/gtk4/class.Settings.html#properties
These files are located in $HOME/.config/gtk-3.0/settings.ini usually.
This is more or less a repost of this post: https://github.com/geany/geany/discussions/4509.