Credentials record attendance and completion, which are real but narrow facts. They tell someone you were present and met a standard, and they say nothing about whether you can produce anything once the structure is removed. That gap is why two people with identical certificates can be wildly different to work with.

Build one thing that exists outside a course and can be looked at. It does not have to be impressive, only finished and yours. A small working object answers questions about you that a line on a page cannot.