<button onclick="showContent()">نمایش محتوای مخفی</button>

<template>
    <h2>گل</h2>
    <img src="https://www.bubbleslearn.ir/wp-content/uploads/2021/07/img_white_flower.jpg" width="214" height="204">
</template>

<script>
    function showContent() {
        var temp = document.getElementsByTagName("template")[0];
        var clon = temp.content.cloneNode(true);
        document.body.appendChild(clon);
    }
</script>