Hi @RenatoT thanks for reaching out us.
Can you please:
add a tag to specify the C4D version you're using?
can you make use of the Q&A functionality?
With regard to HandleShaderMessage, I confim that it is indeed used by shaders in NodeData::Message() when they have subchannels. The code snippet found the call documentation represents exactly what is used in the Fusion shader with regard to the Base, Mask and Blend channels.
Instead with regard to SHADERINFO_DYNAMICSUBSHADERS, assuming I've checked the version of Cinema you're working with, it is used no more.
Looking forward your further notes, give best.