I'm trying to remove meta boxes added to the WordPress menu editor page from a theme, but can't seem to figure out how to do it, I found this answer, but I must be doing something wrong as it isn't working.

Below is what I want to remove:

My code:

add_action( 'do_meta_boxes', 'blm_remove_plugin_metaboxes' );

function blm_remove_plugin_metaboxes() {
    remove_meta_box('_menu_icon', 'nav-menus', 'side');
}

For the ID I have tried the following but none have worked:

• _menu_icon
• menu_icon
• add-_menu_icon
• add_menu_icon

Trying to find the code in the theme files that adds them, it appears they are utilising these hooks:

add_action( 'wp_nav_menu_item_custom_fields', array( __CLASS__, '_fields' ), 10, 4 );
add_action( 'wp_update_nav_menu_item', array( __CLASS__, '_save' ), 10, 3 );
add_filter( 'manage_nav-menus_columns', array( __CLASS__, '_columns' ), 99 );

The class method _fields appears to then call the respective method for the type of field and then echos that data.

Am I missing something?