I've moved this to the wishlist as it is indeed currently not possible. I've also added it to our customer wishlist. However, since it is already available by editing the html. This will most likely have a lower priority.
For anyone else wondering. You can display the HTML code by using the icon displayed in the screenshot below. Then you can use the following HTML code to make a table.
<h2 style=";">Cell that spans two rows:</h2>
<table style="width:100%;" border="1">
<tbody style=";"><tr style=";">
<th style=";">Name:</th>
<td style=";">Bill Gates</td>
</tr>
<tr style=";">
<th rowspan="2" style=";">Telephone:</th>
<td style=";">55577854</td>
</tr>
<tr style=";">
<td style=";">55577855</td>
</tr>
</tbody></table>