Thanks! That looks exactly what I am looking for. I’ll try it this afternoon :-).
By the way, it may be handy for CSS-noobs like me (but I have seen a lot more noobs on this supportforum when I searched for this) to make a help-page or examples-page with the 20 most common things to do with custom CSS on GeneratePress. I couldn’t find it at the plugin-page on WP and also not on this website, but maybe I didn’t search well enough.
Just a suggestion :-).