We can re-create existing ones from known (small) genomes and make some modifications to ones that we understand well. Even that work is well beyond what a hobbyist can achieve. Creating a novel virus would be a major research project.

There is a lot more work on synthetic viruses that you might not be aware of that goes beyond just simple instantiation (like viral attenuation for vaccines or hypotheses on origins of the viral outbreaks). Creating a novel virus these days is not that diffult (Grad student project). Anyways, your first post made it seem like it hadn't been done.

I'm not aware of every paper in the field, but I know the high points. We're still a long way off from the day when niche groups can generate novel viruses with specific infective properties. We're still basically just tinkering with the existing viruses in labs to figure out what the parts do.

Depending on how you define "novel", it could indeed be a "grad student project", or it could be a paper that deserves a Nobel. But it still falls firmly in the "improbable as a weapon" category of threats. I'm still far more scared of XDR TB than hypothetical synthetic viruses.