How to add mesh groups and link them to different images?

I don't use to making CC but sometimes I like to make things for my personal use with Sims 4 Studio, I've tried to make my own CAS but I don't know how to add mesh groups and have them linked to different images, I could only duplicate a mesh group with TSR Workshop but it won't let me put a different image, it just replaces the image in all the mesh groups, I don't know how to do it correctly.

I could use a CAS from another creator and replace the mesh/images but it has happened to me many times that I need to add a mesh group and I don't know how.

I don't know how to find a solution anymore, I hope someone knows and can explain it to me. Thank you.