Add to structured data remove from structured data from the front end

The CMS Questions
2

Check if an entry exists in the collection:

$items = $page->yaml_field()->structure();

$item = $items->findBy('title','cats');
if($item) {
  // do something
}

Add to structure:

    function addToStructure($page, $field, $data = array()){
      $fieldData = page($page)->$field()->yaml();
      $fieldData[] = $data;
      $fieldData = yaml::encode($fieldData);
      try {
        page($page)->update(array($field => $fieldData));
        return true;
      } catch(Exception $e) {
        return $e->getMessage();
      }
    }

Removing items: use unset[‘key’]

See this post: Delete fieldentry from frontend?