[TWC] Substitution marker in hidden section

[Jay]

In a classic TW, I would like to have a single tabset template with tab content based on a tiddler's title, which I thought I could do with a substitution marker as in the sample below. Apparently, the substitution marker isn't replaced in the hidden section. The tab name is correct ("Test Tab"), but its content is "$1," no replacement. Is there a way to do substitution in a hidden section? (Or alternatively to have the tab target pass along the value of $1 to another tiddler?) Thanks!

Template tiddler, named Tabs:
<<tabs t "$1 Tab" tooltip "Tabs##content">>
/%
!content
Content: $1
!end
%/

Transcluding tiddler:
<<tiddler Tabs with:Test>>