This is the same for me. I just posted a thread on the official Apple forums about this:
=====
discussions.apple.com/thread/253758044
Wi-Fi AP order not accepting change - "Drag networks into the order you prefer" not working across both my Macs
My MBP16 and iMac 27 running 12.3 are both connecting to one Wi-Fi network, when I need it to connect to a different one. So,
1) I open System Preferences
2) click on Network
3) select the Advanced button in the lower-right corner
4) select the Wi-Fi tab at the top
5) grab and drag one access point/SSID to a different spot on the list
6) click OK
7) click Apply
8) then click the Advanced button once again just to check that the order has changed -- AND IT HAS NOT! The network order cannot be changed by dragging the networks into the order I prefer.
A reboot does not affect this. (How could it? The list isn't even changed before a reboot.)
It happens on both my Macs.
It happened prior to 12.3 as well.
Changing both Macs at the same time doesn't work either.
One partial workaround is to remove a network and then to re-add it. That one network is then moved to the top of the list, but I can't do that with all my networks. I see some of them only once a week. It would take me months to get them in the order I prefer.
I think this is clearly a bug as it is a simple operation and it is happening across two different Macs.
Even if this were to work, the list shows only 5 networks at a time, and trying to drag one more than four spots results in the list quickly scrolling to the end. That is broken as well, though with enough time, you can work around that.
=====
I'll submit a bug report to
www.apple.com/feedback/ as well.