In order to achieve this:
Make sure the defect quotes are on the same property/client
On a draft quote, click Other quotes
Select the defect quotes you'd like to merge
Click Merge lineitems and Void
This will then merge the original quotes and Void them
Please be advised of the following when merging defect quotes:
Merging quotes will copy all lineitems except:
lineitems attached to remarks that have been resolved
lineitems on quotes that have been approved/actioned
It is not possible to merge defect quotes from different properties
subsequently, it is not possible to merge defect quotes from different clients