Very good plugin, thank you!
Found a problem: the result of Recompute Normal in Object mode cannot be saved after restarting the editor. But the results of Assign Smooting Group in Quad mode can be saved.
In addition, is it possible to implement an edit vertex normal function similar to that shown in this video (Softimage Plugin: User Normal Translator - YouTube)?
Editing vertex normals can be called the ultimate demand for anime-style cel shading.