You can currently add a definition to any ObjectType or FactType using the ORM Definition Window. There is a display option on the ORM Designer options page to display the definitions as tooltips. They will also show up as additional reports.
The Definition and Notes windows are currently text only. We are open to adding other forms, including definition hierarchies, as future features. The main usability enhancement for these windows needs to be buttons in the toolwindows to commit the change. You current need to move focus off the window to commit the change, which is a clunky gesture.
You'll see gradual improvements in column naming in the next drop. Specifically, explicit phrase mapping (in addition to object type names) will be added, and column name generation for identifier columns and columns with multi-step FactType paths (included absorbed column names) will be added as well. Future drops will also include dialogs for the reverse perspective of the current Name Generator Settings Abbreviations dialog, where all abbreviates for a given ObjectType will be visible from the ObjectType. The current dialog requires you to choose a name generation context and specify abbreviations at that point.
-Matt