I’m new to WordPress myself, but I think answering questions is a good way to learn. There may be a way to use hooks, but I couldn’t figure that out, so went ahead with directly editing header.php.
I tried the following:
From Appearance, Menus, I added a new menu and named it Vert_Menu_test
I chose to add the menu to the top left corner of my test site: In my header.php file, at the very beginning of the body, I added this code (based on this doc)
<?php
$defaults = array(
//'theme_location' => '',
'menu' => 'Vert_Menu_test',
'container' => 'div',
//'container_class' => '',
'container_id' => 'vert-menu-div',
//'menu_class' => '',
//'menu_id' => '',
'echo' => true,
'fallback_cb' => false,
//'before' => '',
//'after' => '',
//'link_before' => '',
//'link_after' => '',
'items_wrap' => '<ul id="%1$s" class="%2$s">%3$s</ul>',
'depth' => 0,
//'walker' => ''
);
wp_nav_menu( $defaults );
?>
I gave the container div the id “vert-menu-div”. (See above.) So, in style.css, I added
#vert-menu-div {
position:fixed;
background-color:#eee;
}
This was enough to get the basics. A vertical menu fixed to the top-left corner. Good luck.