When I exported my project to joomla, I no longer have my library. Why? It's very annoying

When you try to insert one of the blocks from "My library" the applikation hangs - sort of. It tries to import it, but nothing really happens. You kan then quit the program and open it again, and then...

Can someone please advise me how to change the page previews in the left column in the web library (desktop application)? Quite often I use the export / import of a ready-made website and I just...