Hi,
You can use the function post_categories_meta_box() as the callback function of the setting meta_box_cb.
The code should be:
$args = [
'label' => esc_html__( 'Positions', 'irw-position-textdomain' ),
'labels' => $labels,
'description' => '',
'public' => true,
'publicly_queryable' => true,
'hierarchical' => false,
'show_ui' => true,
'show_in_menu' => true,
'show_in_nav_menus' => true,
'meta_box_cb' => 'post_categories_meta_box', //here
'show_in_rest' => true,
'show_tagcloud' => true,
'show_in_quick_edit' => true,
'show_admin_column' => false,
'query_var' => true,
'sort' => false,
'rest_base' => '',
'rewrite' => [
'with_front' => false,
'hierarchical' => false,
],
];
Get more details in the documentation https://developer.wordpress.org/reference/functions/register_taxonomy/.
And refer to this topic https://wordpress.org/support/topic/custom-taxonomies-throwing-error/.
.
