I've actually copied the "Bookmarks" and "Bookmarks.bak" files from Chrome's User Data's path "C:\Users\Stoyan\AppData\Local\Google\Chrome\User Data\Default" to the Opera Profile's path "C:\Users\Stoyan\AppData\Roaming\Opera Software\Opera Stable" and replaced them. It's working pretty well and I think you can do it with most of the browsers.