Another option for merging data files is to use OneDrive (or some other sync agent) to update files on your machine. This does mean everything would be on your PC twice, and it also means that you would have to wait a minute after logging in to sync files, but it would work.
Generally, when dual booting it is because you are trying to move to one OS, but still need a feature or two from the old one. If you need both OSs all the time then you should look into running the less-used OS as a VM rather than a dual boot.