denis_alekss,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<ul id="list1">
<li>Кофе</li>
<li>Чай</li>
<li>Кола</li>
<li>Виски</li>
<li>Коньяк</li>
</ul>
<script>
let li = document.querySelector('#list1 :nth-child(3)')
li.insertAdjacentHTML('afterend', '<li>Водка</li>');
li.remove()
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
</head>
<body>
<ul id="list1">
<li>Кофе</li>
<li>Чай</li>
<li>Кола</li>
<li>Виски</li>
<li>Коньяк</li>
</ul>
<script>
let li = document.querySelector('#list1 :nth-child(3)');
let f = document.createElement('li');
f.append('Водка');
li.replaceWith(f);
</script>
</body>
</html>