JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="element">Element</div>
  <div class="element">Element</div>
  <div class="element">Element</div>
  <div class="element">Element</div>
</div>

SCSS

.container {
  position: absolute;
  overflow-y: scroll;
  height: 400px;
  width: 200px;
  margin-top: 50%;
  margin-left: 50%;
  transform: translate(-50%, -50%);
  border: 1px solid green;
  
  .element {
    height: 100px;
    padding: 10px;
    position: relative;
    margin-top: 10px;
   
     &::after {
       content: '';
       position: absolute;
       top: -20px;
       //left: -30px;
       width: 50px;
       height: 20px;
       border: 2px solid black;
       background: white;
     }
  }
}