The following is not a complete solution, but should get you on your way...
Take a look at [[$:/core/ui/MoreSideBar/Tags]]. You will find these lines that generate the tag pill list output:
<$list filter="[tags[]!is[system]sort[title]]">
<$transclude tiddler="$:/core/ui/TagTemplate"/> <small class="tc-menu-list-count"><$count filter="[all[current]tagging[]]"/></small>
</$list>
First, copy this into a separate tiddler, so you will get just the list without the "tag manager" button above, or the "untagged" items below. Then, modify the filter in the <$list> widget to suit your needs.
enjoy,
-e
Eric Shulman
TiddlyTools / ELS Design Studios
"Inside TiddlyWiki: The Missing Manual"
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