Switch to HTML editing mode in the Shopify editor and manually modify the HTML code to merge cells. Locate the table in the HTML code and use the appropriate HTML tags ( or ) to merge cells using the colspan and rowspan attributes. Here’s an example:
<table>
<tr>
<th colspan="2">
Merged Cells
</th>
<th>
Cell 3
</th>
</tr>
<tr>
<td>
Cell 1
</td>
<td>
Cell 2
</td>
<td>
Cell 3
</td>
</tr>
</table>