I appreciate the steps you've tried, mark_g. I've got a workaround to achieve your goals today.
The Inventory Valuation report is the only report that will provide you the average cost of an item while this can be grouped by Item. You'll want to export this and fix the groupings through Excel. You can add the Pref Vendor and Item as a column on the report.
To add Pref Vendor and Item as a column:
- In the Inventory Valuation Detail page, select Customize Report.
- Select the Display tab.
- Under the Columns field, search Pref Vendor and Item.
- Click on OK.
Once done, you can export it to Excel and fix the groupings from there to get the information you need.
I'd also recommend checking out the customize reports in QuickBooks Desktop for additional guide.
Tag me in a comment below if you have any other concerns on customizing reports in QuickBooks. I'll be right here to help.