Not all APIs are provided yet, please request whathever you are missing.
Some example plugins are provided in demos/plugins. Just copy them to a folder in your project named addons/ and then enable them from the project settings.
Have fun!
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-Ability to set 2D nodes as bones
-Abity to set 2D nodes as IK chains
-2D IK Solver
-Improvements in the UI for adding keyframes (separate loc,rot,scale buttons)
Juan Linietsky
George Marques