This dialog box is displayed if you click Verify in the Quick Migrate box and the database user for the connection does not have all privileges necessary for a multischema migration. For multischema migrations, this user must granted the RESOURCE role with the ADMIN option; and this user must also be granted the CREATE ROLE, CREATE USER, and ALTER ANY TRIGGER privileges, all with the ADMIN option.
If you are performing a single-schema migration, you can ignore this warning.