Setup your query before hand with the fixed value rather than the dynamic to cheat a bit to make it easier:
Set it up normally, invoke it and see what values are in the pipeline after the invoke… Write these down.
Add a MAP step before the invoke to SET that same structure, but turn on “pipeline variable substitution”. Probably easier to copy the input from the query xml node, and then type in the values to get it to the same as would be setup by the WQL tab on the service invoke. Replace your fixed string ‘QV’ with ‘%prodlineNameToSearch%’
Put your QV or whatever into the prodline name to search.
Delete the existing set on the “fields” input of queryXMLNode (otherwise you’ll lose your manually set up “fields”).
Of course you don’t get the funky tab to set it up, but if you don’t change it much I wouldn’t stress… It’s just a helpful way to setup what is after all just a boring input to a service.
See if that does it…