If the consignment is too big to be transported in one vehicle or if there are multiple legs involved in the movement of goods due to transshipment then a multi-vehicle E-way bill is created.
From the left menu click on 'E-way bills' to land on the View E-way bills page.
You will be able to see the list of invoices with E-way bill details (if available) for the last one week by default.
Select the invoice to be updated for multi-vehicle movement.
Only E-way bills which are active and in 'Generated' status can be updated for multi-vehicle movement.
After selecting the E-way bill click on 'More Actions' → 'Update EWBs' → 'Change EWB to multivehicle'.