gtk4/org.gtkkn.bindings.gtk/Gtk/STYLE_PROVIDER_PRIORITY_USER

STYLE_PROVIDER_PRIORITY_USER

const val STYLE_PROVIDER_PRIORITY_USER: Int = 800

The priority used for the style information from $XDG_CONFIG_HOME/gtk-4.0/gtk.css.

You should not use priorities higher than this, to give the user the last word.