Hi Paula
We used the SharePoint Managed Metadata Service (MMS) aka Term Store for a couple of years from 2012 and then used the Enterprise Architecture application that I used for all data modelling and maintaining a single source of metadata 'control' for all our business applications. But I found it was just easier to maintain the BCS/File Plan and associated retention classes in Word.
I also used a Java Script based data visualisation tool, Springy, but this wasn't very useful except for the visual effects.
Andrew