Unless somebody removed it from the templating code (anybody dares to touch that, BTW? 😊, a certain undocumented, experimental, yada, yada feature should work.
Here's an example:
foo.tcl file:
multirow create multi one two
multirow append multi 1 2
multirow append multi 3 4
foo.adp file:
<master>
<include src="bar" &multi=multi>
bar.adp file:
<table>
<multiple name=multi>
<tr>
<td>@multi.one@</td>
<td>@multi.two@</td>
</tr>
</multiple>
</table>
If I understand correctly, this is what you want to do.