That means it created inside ~/.config/gtk-3.0/
the following:
assets/ - folder for the buttons to integrate with the Breeze theme
colors.css - to match the colors of the color-scheme used in KDE Plasma
window_decorations.css - to decorate the windows according to Breeze
This 3 need to be removed and keep just
gtk.css
settings.ini
Log out and back in once you remove the 3 above and all will be back to normal.