clonePreview.js

<script>
	// wait until the complete ribbon is loaded
	TXTextControl.addEventListener("ribbonTabsLoaded", function (e) {
		attachEvents();
	});

	function attachEvents() {
		// store the parent element
		var parent = $("#tglBtnPreviewMergeResults").parent();
		// clone and append the element to the parent
		$("#tglBtnPreviewMergeResults").clone().appendTo(parent);
		// remove the old element
		$("#tglBtnPreviewMergeResults").remove();
		// rewire required events
		$(document).on("click", "#tglBtnPreviewMergeResults",
			function () {
				alert("Custom Preview");
			});
	}
</script>