Custom admin menu order fails if slugs are complicated

I’m not able to reorder WP Admin menu items when pages added with add_menu_page have complicated slugs. At least I think that’s the problem…

First I create the custom menu items, which is working as expected:

function sma_simplify_admin_ui() {
    global $user_ID;
    if ( $user_ID != 1 ) {
        add_menu_page( 'Menu', 'Menu', 'edit_posts', 'nav-menus.php?action=edit&menu=16', '', 'dashicons-menu' );
        add_menu_page( 'Memberships', 'Memberships', 'edit_posts', 'edit.php?post_type=wc_user_membership', '', 'dashicons-groups' );
    }
}
add_action( 'admin_init', 'sma_simplify_admin_ui' );

The new items cannot be reordered. If I put the exact slugs given when they were created, menu_order (and custom_menu_order) simply ignore them and my new items are always at the bottom of the menu.

function sma_reorder_admin_ui($menu_ord) {  
    if (!$menu_ord) return true;
    return array(
        'nav-menus.php?action=edit&menu=16',
        'edit.php?post_type=wc_user_membership',
        /* truncated for clarity, there is more stuff */
    );
}  
add_filter( 'custom_menu_order', 'sma_reorder_admin_ui' ); 
add_filter( 'menu_order', 'sma_reorder_admin_ui' );

Setting a priority when I create them isn’t letting me reorder them either, which is really weird…

I’m theorising the slug expected by custom_menu_order & menu_order isn’t what I’m giving it, but I don’t know what to give it. I’ve also tried every single slug/key/thing that I get when I vardump $GLOBAL['menu'].

Please help me work out how to reorder my menu items!