Hey, that's me
I started that repo as a research project back in the days of Arena 4. It turns out it's way too difficult to get this working reliably.
SVG is an open format, and there's so many ways to store shapes that it's impossible to do any processing on this. This is no problem when you're just displaying shapes, but when you need to create slices based on it, it becomes a mess. For example, all is fine when you just create rects, but when your slice shape is made up of compound paths or separate lines, the importer won't recognise it as a slice. We can't offer such a feature when it only works 10% of the time.
Also you get into so many gotchas and requirements, like input and output slices needing to have exactly the same name or else things break, that it just ended up easier to make the presets in Arena itself.