Hide Text on Window Titles

I need to hide the text on window title headers (titlebar), which usually shows the application’s name or route.
I need this particularly for Blender, which apparently is a non-GTK software.

Which file should be modified for this? Giving the window title’s text the same color as the header’s background would suffice.

I managed to change the titlebar’s height in ~/.config/gtk-3.0/gtk.css.
But I don’t know how to change the titlebar’s text color there. Some say in the metacity theme .xml files, but the default Gnome 43 theme Adwaita comes with no metacity files.