Normally you'd connect using the Bookmark that has the scheduled sync, then cancel the sync from the queue drawer.
Another way would be to move the Bookmark file out of Yummy's Bookmarks folder, since it won't check outside its own folder. Either right-click it in the Bookmarks window (see Show All Bookmarks from the Bookmarks menu) and select Show In Finder, or the Bookmarks folder itself will be located here:
Mac HD -> Users -> yourname -> Library -> Application Support -> Yummy FTP
on some older installations it may be here :
Mac HD -> Users -> yourname -> Library -> Preferences -> Yummy FTP
Either way means the customer has to do it.