By default, Menus and Menu Items that are not assigned to a Menu Location are considered private, meaning they are not exposed in non-authenticated WPGraphQL Queries.
If you want to expose Menus and Menu Items that are not assigned to menu locations to public GraphQL Queries, you can use the following snippet:
add_filter( 'graphql_data_is_private', function( $is_private, $model_name, $data, $visibility, $owner, $current_user ) {
if ( 'MenuObject' === $model_name || 'MenuItemObject' === $model_name ) {
return false;
}
return $is_private;
}, 10, 6 );