The rightmost toolbar group of Rhino 6 is named ‘New in V6’. It lists roughly half of the new commands.
All new commands are listed in this file: https://docs.mcneel.com/rhino/6/help/en-us/commandlist/newinrhino.htm
The file is worth reading because it describes many useful innovations. Links in this file take you to sometimes rough and unfinished descriptions of the new commands.