Определяем на какой странице комплексного компонента находимся

$component = $this->getComponent();

if ($component) {
    $parent = $component->getParent();
    if ($parent) {
        $parentParams = $parent->arParams;
        $engine = new \CComponentEngine();
        $page = $engine->guessComponentPath(
            $parentParams['SEF_FOLDER'],
            $parentParams['SEF_URL_TEMPLATES'],
            $variables
        );
    
        $arResult['TARGET_PAGE'] = $page;

    }
}

$arParams['SEF_URL_TEMPLATES'] = [
    'news' => '',
    'section' => '#SECTION_CODE#/',
    'detail' => '#SECTION_CODE#/#ELEMENT_CODE#/'
];