Any tips on copying learning materials and user histories from Sub LearnCenter to root LearnCenter?

Summary:

My organization is looking to import or copy all learning materials and user learning histories from a Sub LearnCenter into our root (source) LearnCenter so that there will be one LearnCenter for all employees. We used to be considered two separate entities but there is a push now to have everything in one LearnCenter. Currently all users exist in both the Sub LearnCenter and the source (root) LearnCenter, but that is it. The Sub LearnCenter and the root LearnCenter have different learning plans, enrollments, content, etc. Some users have Learn histories in both the Sub and root LearnCenters, as the