gistfile1.aw

<?php

// _config.php

Object::add_extension('SiteConfig', 'CustomSiteConfig');

// CustomSiteConfig.php

class CustomSiteConfig extends DataObjectDecorator {

	public function extraStatics() {
		return array('has_many' => array(
			'Relationship' => 'ClassName'
		));
	}

	public function updateCMSFields(FieldSet $fields) {
		$field->addFieldToTab('Root.TabName', new ComplexTableField(
			$this->owner, 'Relationship', 'ClassName'
		));
	}

}