I use Sashimi too, it's great. You can backup and restore everything from Waze, your account, your preferences, favorites, recent destinations. The files are located in \program files\waze\. You need the following files:
"preferences" (optionally) > program settings (nothing a user can change from the user interface I think)
"user" > account/login, user program options and settings, twitter/foursquare login etc.
"history" > recently found locations (lines that begin with A,) and favorites (lines that begin with F,)
Looking at that last file, it seems that the order of F,-lines corresponds with the order of the favorites in the client. I think yo ucan reorder your favs by changing that file.