From the OpenOCD point of view, ST-Link v3 is backward compatible with the previous versions, so simply selecting one of them on the Debug Settings page should work (you will need to switch from USB Devices view to Debug Methods view in order to do that).
We have also added USB VID/PIDs for ST-Link v3 to the device definitions in our development branch, so the next version of our OpenOCD package will recognize them automatically.