Friends List Sync is a very simple add-on that will synchronize your friends list between all your characters that are on the same account.
This means that if you add friends to one character, the next time you go on another character those friends will then get added there as well. Likewise the same goes for when deleting friends. Basically you have just one friends list between your characters now that will always stay up-to-date across all your characters.
There's no options for the add-on, it just happens automatically.
The add-on works with friends list modification add-ons, as it doesn't touch the friends list UI at all.
IMPORTANT - READ THIS BEFORE INSTALLING
The first character you log into with this add-on active will create the initial list that will be synchronized from. This means that other characters with perhaps other friends will have those deleted as the synchronization starts. So make sure to log into the correct character the first time you use this add-on.
When synchronizing a lot of friends it will take some time due to the delay I've built-in between each add/remove. If those weren't there Funcom would block a lot of the requests because they'd be happening too fast. The add-on will however tell you when it's done through the FIFO messages on-screen. Likewise it will inform you how many it's adding/removing when it starts.
If you have an empty friends list stored (the one the add-on stores, not the actual game friends list) the add-on will not do anything. This is to prevent you getting your friends list wiped in case something goes wrong with the settings.