Tabl_ is a spreadsheet interface within Rhino for the viewing, editing, and exporting of object properties. Objects are linked to the spreadsheet in real-time, allowing Tabl_ to automatically update as objects are modified.
Tabl_ takes advantage of the new Eto framework in Rhino 6 to provide a simple UI that runs while you model.
Thanks to @clement and @dale for assisting in explaining how Eto works!