A list of sales invoice line items cannot be derived from Microsoft Dynamics Business Central - unless you hire a NAV/BC developer to write a custom report.
But it is easily available with Popdock.
From the Business Central menu - you can only get a list of Sales Invoice Headers, not lines.
This is the Home Page for Popdock.com - where you can create a custom list, joining multiple data tables: such as Posted Sales Invoices (Header) and Posted Sales Invoice Lines.
To Create a custom list in Popdock.com, Add a Tab, name the list, and follow the steps to choose which lists (tables) to join and on what key to join them.
By clicking on the pencil icon, you can edit a custom list, by choosing which tables comprise it; which fields are required; and can define the relationship (key field) that joins the lists (tables).
This slide shows the fields chosen, to which tables they belong and the key field defining the relationship.
Here is the Edit Relationship window:
Finally, the complete, joined, list of sales invoice lines by customer and item number.
Export it to Excel
Convert the Excel range to an Excel table and pivot however you want.
That was easy.