Humentum strongly suggests using the learner's email address as the user ID. This is the one truly unique piece of information across all members on the shared platform. Sometimes, email addresses change, and you can change the user ID at any time by migrating to a new one.
First, you'll need to create a brand new user ID (follow the directions elsewhere on this site) and then you'll migrate old account to the new user ID. The following tutorial will show you how. Note that only the employee's training record is transferred, you'll need to input the name, email, country, etc in the new UserID when you create it.
Key tips:About 'Migrate ownership records only', Don't check this box, because the training records will not be transferred. If you check the box, only the ownership (course, news article, repository items, etc...) but not the training records will then be migrated to the target user. There is really no scenario this would apply to most of our learners.