I have tried the approach like this :
$item = new WordFragment($docx);
$content1 = new WordFragment($docx);
$content2 = new WordFragment($docx);
$content1->addText('1.1', ['font' => 'Arial', 'fontSize' => 8, 'indent_left' => 10]);
$content2->addFormElement('select', ['selectOptions' => [' 0 ', ' 1 ', ' 2 ', ' 3 ']]);
$content = array();
$content[] = $content1;
$content[] = $content2;
$item->addText($content);
But the text and the form element are still not in the same line. Is there anything wrong with the code?