Set locale

This filter can be used to change the value of current locale. By default, WordPress sets the locale in the admin to en_US. With this filter it can be changed to any locale (e.g. when using a multilingual plugin).

add_filter('es_forms_general_set_locale', function(string $locale): string {
    // Get the custom locale (e.g. from the WPML plugin).
    return $locale;
})