JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table class="order-count">
  <tr class="order">
    <td>Товар 1 <span class="plus">+</span>
    </td>
  </tr>
  <tr class="order_item">
    <td>Наименование 1</td>
  </tr>
  <tr class="order_item">
    <td>Наименование 2</td>
  </tr>
  <tr class="order">
    <td>Товар 2 <span class="plus">+</span>
    </td>
  </tr>
  <tr class="order_item">
    <td>Наименование 1</td>
  </tr>
</table>

CSS

.order_item {
  display: none;
}

JavaScript

$('.plus').click(function() {
	  $(this).parents('.order').nextUntil(".order",'.order_item').toggle();
  });