You can export now only selected folder. But, you can now have only one folder selected ( single selection ). In the future, I will improve this, not only for the export operation, but also for operations like delete selected bookmarks/folders or move them in another folder.

What do you mean by packing as a zip? After exporting the selection, the created file should be packed?

Now, xbelSync automatically creates an archive with any file that it touches and saves the archive in C:\Documents and Settings\<user>\Application Data\xbelSync\backup. You may manage the directory from Options/Backups window. This is a basic management window, it will be improved in a later version.