Demo Code:

<link rel="stylesheet" href="/richtexteditor/rte_theme_default.css" />
<script type="text/javascript" src="/richtexteditor/rte.js"></script>
<script type="text/javascript" src='/richtexteditor/plugins/all_plugins.js'></script>
<div id="div_editor1"></div>

<script>
	var editor1 = new RichTextEditor("#div_editor1");

	editor1.setHTMLCode("<p>Hello World</p>");

	function btnInsertHTMLCode_1() {
		editor1.insertHTML("Time is" + new Date().toLocaleTimeString())
		editor1.collapse(false);
		editor1.focus();
	}
	function btnInsertHTMLCode_2() {
		editor1.selectDoc(false);//collapse to document end
		editor1.insertHTML("<p>Insert a new paragraph " + new Date().toLocaleTimeString() + "</p>")
		editor1.collapse(false);
		editor1.focus();
	}
</script>

<div class="mt-4">
	<button class="btn btn-sm btn-outline-primary btn-pill transition-3d-hover px-5" onclick="btnInsertHTMLCode_1();return false;">insertHTML at a specified position</button>
	<button class="btn btn-sm btn-primary btn-pill transition-3d-hover px-5" onclick="btnInsertHTMLCode_2();return false;">insertHTML at the end of this document</button>
</div>