The sidebar search AND the tabbed lists below it are defined the $:/core/ui/SideBarLists shadow tiddler
*Most* of the content in that tiddler is for the search handling. What remains is for the tabbed lists. You can remove the search stuff, leaving just this:
<div class="tc-sidebar-lists">
<$macrocall $name="tabs" tabsList="[all[shadows+tiddlers]tag[$:/tags/SideBar]!has[draft.of]]" default={{$:/config/DefaultSidebarTab}} state="$:/state/tab/sidebar" />
</div>
enjoy
-e
Eric Shulman
TiddlyTools / ELS Design Studios