Mastery of what topic? What I consider important for my work in safety critical systems is probably very different from whatever you use in your presumably diff

Mastery of what topic? What I consider important for my work in safety critical systems is probably very different from whatever you use in your presumably different field. Both of those are different again from e.g. GameDev, HPC, or operating systems and all of them encompass domain knowledge not adequately captured by existing degree programs. How would a useful certification be realized, as opposed to mere credentialism?