It is possible to import Summary Lines & Sub Total Lines in your Sales Transactions for QuickBooks Online using the SaasAnt Transactions (Online) application.
Importing Sales Transactions with Summary Lines in QuickBooks Online
Kindly map your Summary Line to the "Line Description" field. The particular line should not have any Amount of fields (Line Item Amount, Discount Amount ).
The particular row which has Summary Line should have the information like the below image
It will be reflected in QuickBooks as below.