Isso deve resolver.

```html
<!DOCTYPE html>
<script>
    const criarMaisUm = (maisUm) => {
        const itemsElemento = document.querySelector('#items');
        if (maisUm == 'sim') {
            itemsElemento.innerHTML += `<label for="item">Item</label><input type="text" id="item" name="item" required><br>`;
        } else {
            itemsElemento.innerHTML = '';
        }
    }
</script>

<html>
  <form>
    <label>Mais um?</label><br />

    <label for="mais-um-no">Nao</label>
    <input type="radio" id="mais-um-nao" name="grupo-mais-um" value="nao" onchange="criarMaisUm(this.value)">

    <label for="mais-um-yes">Sim</label>
    <input type="radio" id="mais-um-yes" name="grupo-mais-um" value="sim" onchange="criarMaisUm(this.value)">

    <div id="items"></div>
  </form>
  <script>
  </script>
</html>
```

Isso deve resolver. const criarMaisUm = (maisUm) => { const itemsElemento = document.querySelector('#items'); if (maisUm == 'sim') { itemsElemento.innerHTML += Item; } else { itemsElement...