Copying Group Members From One Group to Another

It would be great to be able to copy membership access from one group to another. Better yet, if we could add members to a group manually as an admin. 

Use Case:

We have an employee user group that really took off recently. So much so we want to create another group focusing on a different topic. I’d like to be able to copy/paste the existing membership base of Group A into Group B. In doing so, it would really help with adoption I think.