ExtConfTemplateHelper::textfield() 

\nn\t3::ExtConfTemplateHelper()->textfield($conf = []); 

Show multiline text field / textarea in the Extension Manager configurator. Use this line in ext_conf_template.txt of your own extension:

# cat=basic; type=user[Nng\Nnhelpers\Helpers\ExtConfTemplateHelper->textfield]; label=My label
myFieldName =

| @return string

public function textfield( $conf = [] ) {
	return "<textarea style=\"min-height:100px\" name=\"{$conf['fieldName']}\" class=\"form-control\">{$conf['fieldValue']}</textarea>";
}