Hi Charlie
Because rather than keep on adding new tables to Recorder as new termlists were required, we took a decision to use a thesaurus model which allows the storage of multiple lists in one piece of the database. These lists support hierarchy and synonymy as well as things like multi-linguality and some other features not shown in the user interface. Although not used in the observations window to keep things simple, tag hierarchies could still be used in your custom reports.

Best Wishes