Hi @yblanchard,
Sorry for the delay, and thanks for posting here, that’s a very good question!
Regarding the carbon fiber modeling here you have the answer:
Regarding the local reinforcement like embedded elements technique in Abaqus, e.g.: Additive Manufacturing, it is not available inside SimScale platform as well. Particularly for me it is a good question once I’m reaching this same subject for metallic alloys in my masters degree, so for that gross approximations could be done using the right contact between the embedded and host region, but not sure about the error rate so it can be a good theme for another topic/study. 
Best,