arfavailablefields

add_filter('arfavailablefields', 'your_function', 10, 1);

function your_function($form_elements){



    //Add field in basic form elements list at form editor.

    $outside_field = array(

        'FIELD-TYPE' => array(

            'icon' => 'FIELD ICON',

            'label' => 'FIELD LABEL'

        )

    );



    return array_merge($form_elements, $outside_field);

}