That's right as far as I am aware, but I heard they are working on improving how it works as it is still in beta. I think they need to be think carefully about how it interacts.
What I plan to do is make a library of slices and then import them at the start of a project, although I haven't tried this yet.
Unfortunately, after the initial setup that I think (for the time being) we will have to do it the old fashion way of keeping everything in a big json file ready to copy and paste.
Edit: Doesn't seem to allow you to use any other libraries than the ones registered/uploaded to Prismic. Shame, while I want to contribute I am not ready for it to be public.