Except for encrypted memos and maybe encrypted content that can is stored as custom_json transaction. One of the cool features of the Hive wallet is one owner transacting with another owner can send them encrypted memo, that only people transacting with each other see. For example if I sell something to someone, I would be able to send an invoice that they only see the order details.

is anybody doing work on this? Feels like we have a feature here that has yet to be utilized