I can see what you mean about the tags, which is why I added the "maybe not?" at the end, it could get quite messy. So are you saying you can't add new and edit collections on the Sony the way you can add/edit shelves on the Kobo? Or do you just find it's easier on the Kobo?
BTW, off topic, every time I glance at your avatar I think you have a dog whose front half is one colour and the back another... and possibly a big backside - then I notice the backside has ears, an eye and nose and it all becomes clear
