I just noticed today the "tag" attribute for Checkbox Widgets.
That is a huge help putting together a custom interface for managing tags on any tiddler.
So thanks to whoever worked on that little gem.
Snapshot below of a work-in-progress (part of a modal window for editing tiddlers).
aside: Not noticeable in the screenshot, each of the "fieldset" elements have vertically scrollable content, just to take a less real estate.
Cheers!