This is actually easily done. I just adapted the code from this answer
add_action( 'admin_bar_menu', 'customize_my_wp_admin_bar', 80 );
function customize_my_wp_admin_bar( $wp_admin_bar ) {
//Get a reference to the view-site node to modify.
$node = $wp_admin_bar->get_node('view-site');
//Change target
$node->meta['target'] = '_blank';
//Update Node.
$wp_admin_bar->add_node($node);
}
To change any other item in the menu bar you just need to find the id of the item to change and adapt get_node
. Look in /wp-includes/admin-bar.php
for the id or have a look at the css classes of the output.