(Temporary?) fix? Copied FCP_SMT_232_HSSE_Flux_Presets.vstsound to where I store my Halion Sonic SE libraries. Double-clicked, registered it with the Halion Library Manager, restarted Cubase, and they show up.
The .vstsound is in the update files at Steinberg\WIN64\Cubase Pro 9.5 - Update from 9.0\Cubase 9.5\Cubase for Windows\Additional Content\VST Sound\PresetVSTSound