At this time we do not offer the option to merge two accounts together. All course progress that is earned is tied to the account that it is earned on.
While this is not a feature that we currently have, you can always request features through our suggestion board. We can't promise that every request or even any specific request will end up being created, but we do look at each and every submission, comment, and vote to ensure we are working on the content that students like you most want to see!
Check there to see if these have been suggested already and feel free to add them if you don't see them!