The option to have one Master Item created which in turn, links items that are assigned to the same Customer Account and Item Type is available in Versions after 8.521.
A tickbox indicates if the Item is a Master Item
Once a Master Item has been created, all Items of the same Type can be selected for the Customer by using the dropdown selection in the Master Item Link.
A Master Item will not be able to be deleted until all Child Items are reassigned.
Invoicing Job's with Master Item Links
If a selection of Jobs are done with the same Master Item link are done,
They can be invoiced at the same time, using the Bulk Invoice Job's, and select Job's with assigned Customer Items linked to Master Item.
Select the Master Item from the drop down list.
The invoice setting will be populated as the above screen. The invoices will be saved as pending Invoices.