About a decade ago, PTC had an accreditation program. It was mostly based around Proficiency tests (the multiple choice tests you now see in the Precision Learning Management System) and some short modeling exercises. But it never really took off.
But Bogdan is correct, there is no official certification program.
Yes, it is sad that Creo does not offer certification, I have looked myself in an effort to have official evidence that I do CAD! The next best thing is to try and make a portfolio of some sort. PTC does offer certification for some of their IOT and AR products here though, if you are interested https://www.ptcu.com/
Agreed, Omar, either previous employment or a portfolio are the only ways of proving that you have any kind of expertise. The problem with portfolios is that often the work you do as an employee is covered under intellectual property or non-disclosure agreements.