the current version of the RTF Filler component available on the Add-Ons Store supports a subset of the available XHTML tags.
The subset of the available XHTML tags that can be used to fill the RTF template is reported below:
Ordered list <ol>
Unordered list <ul>
List item <li>
Default cell <td>
Header cell <th>
If you want to obtain your result you can try to extend the component and implement this feature.
For more detail about the structure of a RTF document you can refer to the Rich Text Format (RTF) Specifications available in Internet.
Moreover you can refer to these guides: