Check this post

https://www.outsystems.com/forums/discussion/60859/how-do-i-transfer-my-community-activity-and-certifications-from-one-account-to-an/

Hello 

Hello there is a documentation available 

You can check here

https://success.outsystems.com/Support/OutSystems_community/Training_and_certifications_support/Transfer_your_certifications_to_another_account

I hope this helps

Best Regards

Tousif