I found a knowledgeable AAgent who gave me instructions to give a future ticketing or gate AAgent (or AC desk AAgent) to make the proper change as folllows:
"Add QF nyumber using Segment Select FFQF1234567 (insert your QF number there)."
I can't promise automatic results and don't know if this is truly different from how most AAgents would generally attempt this change, but it worked for me recently.
You might find this useful. On QF system the instruction to type into the system to segment relate is (worth printing out for in case you need it) is:
SRFQTVQFHK/-QFXXXXXXX/S#/P#
Where S# is the segment (sector) and P# is the Pax where there are more than 1 on the res (if not will default to single pax)
The following also works on QF to AA (already have LTG and more interested in the miles....)
SRFQTVQFHK/-AAXXXXXX/S#/P#
The common theme is to seg and pax relate the instruction.