Thank you, @Tanaike, for your solution! While my original issue was with inserting a QR code image in the body of a Google Document (replacing a placeholder), the approach you suggested of using getParent().asParagraph().appendInlineImage() and then removing the placeholder element (removeChild()) also worked perfectly for my case. This was after trying many other methods that resulted in the "Element does not contain the specified child element" error. Your solution was the one that finally resolved it. Much appreciated!