Can I add manual tariff rate adjustment linked to an existing SO detail line as detached adjustment?

Requirement: Add manual tariff rate per thousand for an existing SO Detail line based on the quantity from that original line.

I was trying to do this with a detached adjustment (6) but saw in the documentation that this is now allowed for adjustment controls 3 & 6. What are my options to add a manual rate per thousand for the tariff upcharge that adjusts based on the quantity of the SO detail line it's being added to? This needs to print as a separate line on the invoice.