You can convert Online to Desktop or vice/versa and continue to only work in one program instead of both. However, at this time, the ability to sync the two is not available. If you'd like, I can submit feedback to our product development team, so this can be considered in a future update.
Please let me know if there is anything else that I could assist you with. I'll be around the corner to help you every step of the way. You can always reach out to us here in the Community anytime you have questions or concerns. Take care and have a wonderful weekend ahead!