If you want to add id or class for CSS in content editable div, then you will use below code---
<script>
function CssFnctn()
{
document.execCommand('formatblock', false, 'p')
var listId = window.getSelection().focusNode.parentNode;
$(listId).addClass("oder2");
}
</script>
.oder2
{
padding-left: 3em;
}