title: How to create a dynamic divider / separator like JSFiddle
body: <p>I'm working on developing layout for our project and wondering if you can recommend some approach to develop separator or divider which can change size of div's. I'm using CSS FlexBox for div layouts.</p>
  
  <p><img src="https://i.stack.imgur.com/kZPw8.png" alt="enter image description here"></p>