JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.ckeditor.com/4.5.6/full/ckeditor.js"></script>
<h1>Adjacent tables with inline content editable inside TD</h1>
<table border="0" cellpadding="0" cellspacing="0" width="600">
  <tbody>
    <tr>
      <td width="100%" contenteditable="true"></td>
      <tr>
  </tbody>
  <table>
    <table border="0" cellpadding="0" cellspacing="0" width="600">
      <tbody>
        <tr>
          <td width="100%" contenteditable="true"></td>
          <tr>
      </tbody>
      <table>

CSS

td[contenteditable="true"] {
  background-color: #f2f2f2;
  border: 1px dashed #ccc;
}

JavaScript

CKEDITOR.dtd.$editable.td = 1;