conditional visible form field
Try this

$form['call-to-actions-widget']['internal_link']['#states'] = [
  'visible' =&gt; [
    ':input[name="call-to-actions-widget_select"]' =&gt; ['value' =&gt; 'internal_link'],
  ],
];


In case when it doesn't work use another selector 

':input[name="call-to-actions-widget[call-to-actions-widget_select]"]'


Or check in the browser name of the needed field. See e.g. where the name is password[pass1]