I've been using Firefox with the Firefox Account for synchronization, so when i reinstall i cant come back to how i left it, but one things missing, and that's is the Cookie exception List (i delete all my cookies on exit, so i have a hand-made list of adresses where i want cookies to be preserved), this could be saved into the account, or a way to save all the configuration into the account, that way if i just need to reinstall NOT because of errors with Firefox, i can still have all my configuration (when signing in with an account to Firefox, it can prompt if do you want to load the last configuration).
I tried searching for this option if it already exists, but i don't seem to find it.