Use the <$list> widget to transclude each "sub tiddler", like this:
<$list filter="[prefix<currentTiddler>] -[<currentTiddler>]">
<$transclude mode="block" />
</$list>
Note:
This filter finds all tiddlers that start with the title of the current tiddler. This includes the current tiddler.
Of course, you don't want to transclude the current tiddler into itself which would result in this error:
Recursive transclusion error in transclude widget
Thus, the filter also removes the current tiddler from the results,
so that only the sub-tiddlers are transcluded.
enjoy,
-e