Hello Davemarks,
You can use the ‘Visual Data Compare‘ tool to sync only the data that aren’t similar in the source and destination tables by selecting the option ‘Hide similar rows’ in the ‘Visual Data Compare’ wizard. This option presents only the data that has to be synced between the servers excluding the similar data.
Currently SQLyog supports backing up the databases/tables as a whole. The reason SQLyog doesn’t perform backing up only the newly added rows is that SQLyog being a MySQL Client cannot fire queries to the dump file to fetch the data that is already present in it and perform the backup of remaining data.
Regards,
Sibin