I’ve been noticing these for ages but I just assumed they are something techy that Cubase needs to work. But they don’t consistently appear. I’ve just done an import, deleted it from project and pool, then reimported and one - just one (track one if that’s relevant) - has appeared, although 3 tracks were imported. It’s being used, I can’t delete it.
I presume there is a good reason but because only one has appeared I’m scratching my head and seek enlightenment. They don’t half clutter the place up.