Unfortunately I couldn’t find any information on the openSUSE wiki about how to enable WoWLAN.
Same thing with the Arch Wiki.
Luckily, there’s a page on the cyberciti.biz site that details how to activate it, except at the end where it describes the steps to make the change persistent but for a system that appears to use sysv.
As you are on Tumbleweed you are most likely using NetworkManager which supports 802-11-wireless.wake-on-wlan connection setting. I do not know if it is exposed by any frontend, but you can use nmcli to (persistently) set it or simply edit connection definition. It is not specific to openSUSE in any way.
I’m guessing plasma-nm doesn’t expose WoWLAN in the GUI?
I already added a suggestion to the gnome NetworkManager gitlab to expose it, since they already do on the Ethernet panel.
I think it should be exposed on every Network Settings UI no matter the Desktop Environment.