I use Plain Old Favorites add-in for Firefox on my desktop and think it is Fantastic. This add-in works when installed on the PortableApps version of Firefox, however; it still points to the Favorites shell folder on the hard disk.
Does anyone know a way to get this add-in to point to a folder on the flash drive where the other PortableApps are located?
I don't think there is. The whole point of the extension is to use your Internet Explorer Favorites. If you don't use IE, there's no reason to use the extension.
Sometimes, the impossible can become possible, if you're awesome!