Unable to edit taxonomies in Editor

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/.