I've been watching release of J SQ seats each day and usually see Saver seats for SYD-ZRH with availability on flights with good connection times in SIN, and only connection times of 13 or 14 hours for ZRH-SYD, CDG-SYD as discussed earlier in the thread. As Matt_01 suggested, I've seen that the best options were to search for FRA-SYD or LHR-SYD and to book a * Alliance flight to connect to either of those. I had seen several times when searching FRA-SYD with 3 different flight combinations and only one of those with the 13+ hour connection so it looked like that would be a good option for returning back to SYD with shorter connection times in SIN.
However at 11:00 AEDT yesterday the only FRA-SYD Saver fare for Thu 12 Jan 2023 was for SQ25/SQ221 with a 13hr50 connection time with the other two options saying "Saver not available". I've looked at 11:00 today and for the date released today - Fri 13 Jan 2023, there are no Saver fares listed at all for the following routes, with only the Advantage column for 150K showing. Other times I would see Saver not available or Saver - waitlist but today nothing at all: ZRH-SYD, FRA-SYD, SYD-ZRH, Even LHR-SYD only shows 2 Advantage flights listed and both are waitlisted.
From your experiences of booking with KrisFlyer miles - does this happen often? Is there a pattern of SQ not releasing as much Saver availability at different times, possibly on certain days of the week? When I was using the BA site to check award availability when I thought I would book through CX with Asia Miles I could see that BA were releasing 4 x J seats for each long haul flight that I was searching for, although they would usually be gone within a few minutes. I'm still learning about SQ KrisFlyer award bookings so I appreciate the advice I have been given here.