Originally Posted by
Cryotia
I'm trying to do something similar right now. I have a confirmed booking SIN-FRA SQ saver award (booking class I) and want to add an FRA-MUC connection on LH. An hour on the call center resulted in variations of "it's not allowed", "I can't see the availability" (you can find it online on the SQ or any *A website), and "I can see it but it's only in economy so I can't ticket it." They also refused to escalate me to someone who could help out.
This was a couple of years ago for me (2019). I wanted SIN-NYC (forgot if it was JFK or EWR)-WAS (any Washington DC area airport). Space was available for both segments (on the SQ website), but the only way I was going to get NYC-WAS was a separate booking AND SQ could not combine/link PNRs. The miles required for the NYC-WAS segment was quite high as I recall and I just ended up booking with UA directly.