Can United add a segment to the beginning of an award ticket after it is booked? For example, I see much better availability for last minute LH F space LAX to FRA than SFO to FRA. But for some reason, the online tool often does not show the SFO-LAX-FRA-XXX routing. So I was planning to snag the LAX-FRA-XXX LH ticket when it pops up, and then call UA to add the SFO-LAX segment afterwards. Would they do it or would they force me to redo the ticket and thus risk losing the LH F space.
I ask because it is often easier and faster for me to snag a ticket online than call UA.