Noticed problem #5 too : "delete" not working. Instead the library window moves up one level, for example from "characters" to "libraries".

No, that's just a focus thing which also happens in P6: If you click delete while the library has the focus, you just go up a level. Allows for keyboard-only navigation in the library.

But the real delete bug exists, I have it too. Apparently it seems to happen after rendering. Deleting from the hierarchy menu still works.