{{click element}} in tag templates

Question

I want to create a variable in GTM which returns the element which is closest. In a javascript tag it can be done this way:

function() {
  return function(target, selector) {
    while (!target.matches(selector) && !target.matches('body')) {
      target = target.parentElement;
    }
    return target.matches(selector) ? target : undefined;
  }
}

To make our website CSP compliant custom JS tags aren't allowed and we should create gtm variable templates.

The issue with a GTM template is you are not able to pass {{click element}} so I am looking for a method on how to access gtm.click from the datalayer and execute the closest function on that. https://www.simoahava.com/analytics/custom-templates-guide-for-google-tag-manager/#restrictions-to-what-type-of-data-you-can-handle

Is the only way I am able to do this by injecting a script? I would rather fix this by using one of the gtm template api's.