For that you will need to wikify the content of the tiddlers:
<$list filter="[all[tiddlers]!is[system]!is[current]]">
<$wikify name="content" text={{!!text}} >
{{{ [<content>search[desu64]then<currentTiddler>] }}}
</$wikify>
</$list>
The wikify widget will turn the content of each tiddler into its rendered text, that you can then search with a filter. Another way to do that would be to first search for your content, find the title of the tiddler transcluded then search for that tiddler, that way you wont need to use wikify (which is slow).
<$edit-text field="search"/>
{{{ [search:text{!!search}]:map[all[tiddlers]!is[system]search:text:literal<currentTiddler>] }}}