如何：从外部阴影主机将元素插入阴影DOM？

Question

据我研究过，只能将元素插入阴影主机内的阴影dom。

示例：

<div id="myShadowHost"><h1>This is my host</h1></div>


<script>
//attach a shadow to myShadowHost
var myHost=document.querySelector('#myShadowHost').createShadowRoot();
//Declare an insertion point 
var content = document.createElement('content');
//select element to pull into the insertion point, in this case the h1
content.setAttribute('select', 'h1');
//append to shadowHost the insertion point and pulled element.
myHost.appendChild(content);
</script>`

最终，我想进入阴影主机之外的阴影元素。