When I activate my plugin (register_activation_hook), I add a new specific page and a corresponding item menu in the custom menu. No problem here.
When I deactivate my plugin (register_deactivation_hook), I delete the specific page but I don’t know how to delete the corresponding item menu from the custom menu?
WordPress automatically handles that if you force delete the page instead of thrashing it.
The following function takes a parameter to force delete ->
wp_delete_post( $postid, $force_delete )