Additional info on the zone expanders. Support for this was just announced in the IQ4 4.1 firmware details: Qolsys IQ Panel 4 Firmware Release Information - #4 by tyler
This indicates that firmware 1.2 is required on the PG9WLSHW8 though, and the ones I ordered last week shipped with 1.1 and I’m sure your unit does as well.
I found this older post where someone asked how to upgrade an existing unit to 1.1 and was ultimately told “we can’t help you”. I have inquired in that post about Surety’s official stance on how their customers can keep their PG9WLSHW8 modules up to date: How to update PG9WLSHW8 to V1.1? - #7 by Carlisle