The feature is not supported, but you can save the reports in CSV format and manipulate the data in Excel.
Here is one approach:
(1) Open the Inventoria "Inventory" report. Go to Report -> Save as CSV and save it.
(2) Open the Copper "Item: Sales" report. Go to Report -> Save as CSV and save it.
(3) Open the Copper "Item: Refunds" report. Go to Report -> Save as CSV and save it.
(4) Open all three files in Excel.
(5) Also open a blank file in Excel.
(6) Copy and paste the tables from the Inventory, Item Sales, and Item Refund reports into the new table. Paste them side-by-side with a column between each one.
(7) You now have three tables, side-by-side, on a single Excel sheet. If you want, you can insert a top row and label them as "Inventory", "Sales", and "Refunds".
(8) Select and highlight in bold the columns that will matter. These are "Item" and "Item Code", "Cost Value", "Disc. Value" (the price after discounts), and "Qty".
(9) Make sure the Item Codes match up on all three tables, so that an item is on one row. You may need to move the refund values down to the correct locations.
(10) Create a new column, "Net Sales", to the right. It is calculated as the Sales table "Disc. Value" minus the Refunds table "Disc. Value", or =M2-S2
(11) Create a new column, "Net Cost" to the right. it is ((Sales:Qty)-(Refunds:Qty)) * (Inventory:Cost Value), or =(K2-Q2)*F2
(12) Create a new column, "Net Profit" to the right. It is "Net Sales" - "Net Cost".
Then add column totals and any other calculations you need.
I hope that helps, even if it's not as easy as it could be.