title: Insert item in list after two elements
body: <p>I have the list</p>
  
  <pre><code>[%{A: %{}}, %{B: %{}}, %{C: %{}}]
  </code></pre>
  
  <p>how could I add <code>%{D: %{}}</code> between <code>B</code> and <code>C</code> based not in the index, like this:</p>
  
  <pre><code>[%{A: %{}}, %{B: %{}}, %{D: %{}}, %{C: %{}}]
  </code></pre>