ExtData holds your unregistered GQ Pool, Guild Cards and Event Quests.
Since the method to get JP DLC got recently shut down, maybe if someone uploaded their Extra Data, decrypted through SaveDataFiler we can all freely share it with eachother?
edit: Can confirm that this works, someone uploaded their extdata for all of us to share with eachother.
It works in GW Classic Mode, which means it can work on a physical cart of 4U.
The file is uploaded somewhere below in this thread, and theres also another one on that other site we should not mention. Just replace "quest1" to "quest5" from your 4U Extdata and reimport it back with the new ones and you'll be set. You dont lose any of your GC's, and nothing breaks at all