<div class="tc-table-of-contents">
<<toc-expandable "Contents">>
</div>
That is it calls the macro toc-expandable
In advanced search Shadows we find this is in
$:/core/macros/toc
Which on editing we see the definition
\define toc-expandable(tag,sort:"",itemClassFilter:" ",exclude,path)
<$vars tag="""$tag$""" sort="""$sort$""" itemClassFilter="""$itemClassFilter$""" excluded="""$exclude$ -[[$tag$]]""" path="""$path$/$tag$""">
<ol class="tc-toc toc-expandable">
<$list filter="""[all[shadows+tiddlers]tag[$tag$]!has[draft.of]$sort$] -[[$tag$]] $exclude$""">
<$list filter="[all[current]toc-link[no]]" emptyMessage=<<toc-expandable-empty-message>> >
<$macrocall $name="toc-unlinked-expandable-body" tag="""$tag$""" sort="""$sort$""" itemClassFilter="""itemClassFilter""" exclude=<<excluded>> path=<<path>> />
</$list>
</$list>
</ol>
</$vars>
\end
If you look in the define line you can see mention of parameter that appear not fully documented. and exclude is simply added to the end of the filter.
Perhaps trying providing your own exclude parameter, perhaps even to include something +[[tag]]
But I ask do you really want a TOC macro here, because the TOC requires each tiddler be tagged with a tiddler higher up in the tree, and eventually the root tiddler, is this still true when you try and exclude one of your tags?
Regards
Tony