Quote lines allow you to populate existing quotes with task and product lines in bulk via a csv import template. You can upload lines to multiple quotes in the one quote line import. The import template can be uploaded on the imports dashboard (Administration -> Imports).  

Quote Lines Import Field Definitions

TaskOrProduct
Determines type of quote line.  Task or Product
Required
QuoteNumber
Quote number to assign the lines to.  Repeats per line assigned to that project
Required
Sku
Product code for product lines.  Not required for task lines.  If the SKU does not match to an existing product, it will be added as an adhoc line.
Required for product lines only
Name
Task or product name.  If the task name does not match to an existing task,  it will be added as an adhoc task.
Required
Description
Line description

Quantity
Line quantity.  Must be a number
Required
SellPrice
Line sell price.  Must be a number
Required
CostPrice
Line cost price.  Must be a number
Required
Billable
Line billable status. True or False
Required
TaxType
Line Xero tax code.  Usually either GST on Income or GST Free Income
Required