New 2.3 features have not yet been added to the comprehensive functional specification. This will be done shortly.
The 2.2 gradebook release largely included improvements that did not have a direct impact on end user functionality, hence the 2.1 release documemtation still gives the most complete picture of the application.
Information about the 2.3 release
...
Gradebook 2.1 Functional Requirements Notes
Functional Design information for the 2.0 release.