Exclude taxonomy term from select list on node add page
You need to implement hook_form_alter(&amp;$form, \Drupal\Core\Form\FormStateInterface $form_state, $form_id) inside a custom module.

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Form%21form.api.php/function/hook_form_alter/8.2.x

Inside the form parameter you should be able to unset the specific option that you don't want to be displayed.