Where to put #Ajax Callback in webform twig file I would like to add the Ajax callback settings to my custom composite webform element in the twig file.  Is this possible?  The callback function is in my custom module.  This is NOT a computed twig situation.  The Webform is created entirely from D8 webform GUI.

Custom composite has qty, code, description, price.  Using the callback to verify code and update the description and price.
Could something like below be put in the twig file?

'#ajax' =&gt; (
    'callback' =&gt; 'validate_srvform_items',
    'event' =&gt; 'change',
    'progress' =&gt; array(
      'type' =&gt; 'throbber',
      'message' =&gt; t('Populating line item...'),
    )
You can create a form alter function in your module file and then add the callback property to the respective field 

$form['actions']['submit']['#ajax'] = [
  'callback' =&gt; 'callback',
  'event' =&gt; 'click',
];


See also


Alter Ajax callback on Webforms
How do I add an AJAX action on a select element in a ContentEntityForm to change the value of another select element
Update webform field value using AJAX realtime