I appreciate you taking the time to ask this question, @wesnfl. Your question addresses a critical aspect of data migration, and I'm here to provide details to assist with your transition.
The QuickBooks migration tool is designed to transfer transactions not already present in QuickBooks Desktop (QBDT). However, duplicate entries may occur if transactions are imported from QuickBooks Online (QBO) and manually entered into QBDT during migration.
You can find more information about how the migration tool works in this article: QuickBooks Desktop Migration Tool FAQ. It provides answers to commonly asked questions about the utility.
Furthermore, I suggest bookmarking these articles to offer detailed information on data migration, potential limitations, and best practices for a smooth conversion.
The QuickBooks Community team is always here to support you throughout your transition. Should you encounter any challenges or have additional questions about the migration process, add a reply to this thread or create a new post. We're committed to assisting you every step of the way.