Boomi NetSuite connector can import only objects listed under 'Schema Browser" tab.
The reason being - for example, TRANSACTION_LINES could exist only for specific transaction types and this kind of conditional nesting cannot be supported by NetSuite connector.
Objects listed under 'Connect Browser' tab can be obtained via a database connector with JDBC or ODBS connection.
Below is the link which refers to NetSuite objects and support by NetSuite:
"Connector Browser" refers to the ODBC connector while the "Schema Browser" refers to the SuiteTalk API.
To connect to Connector Browser through the Database Connector you need to select the driver type as custom.
Please find the below links to find more about the Database connector
Transaction objects in SuiteTalk do have line items but first we will need to determine if the information we are looking for can be obtained through the SuiteTalk API, otherwise use the database connector.