You might try using a Sales Kit for product XYZ.
This should work for you:
Inventory Item: ABC
Sales Order Item 1: ABC
Sales Order Item 2: Sales Kit XYZ
Sales Kit XYZ consist of:
>>Inventory Item ABC
>>Certificate (optional but may be worth calling out to note the fact that it exists)
When you sell Sales Kit XYZ your ABC inventory will be decremented by 1. The sales order will show the Sales Kit and the detail of the items in the Sales Kit.
As always, try this in your test instance first. Mileage may vary.
Jim
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