If you plan to reinstall Windows or move to another PC, you can backup all your websites from “site manager” and not have to recreate them later.
Open Filezilla, File > Export > check “Export Site Manager entries” > ok > save the xml file on your desktop.
To import your site manager, simply click on File > Import > locate and select the xml file (the backup).
If you have like 40-100 websites in your site manager, it would be really painful to have to recreate all of them by entering the hostname, username and password.