Why are some NetSuite objects missing from the Netsuite schema?
Check the NetSuite Supported Entities article for a list of NetSuite objects that are currently supported. Contact support if any needed objects are not on the list.
If an object is on the NetSuite Supported Entities list and you still don't see it in the NetSuite schema, make sure you have enabled permissions to that object on the Role that is associated with the NetSuite user that is configured with the NetSuite synapse.