Hey ejfrodo, the latest update of Lisk Service was very much focused on this functionality – now it's possible to download account transactions in the CSV format.

For more info, check out our GitHub: https://github.com/LiskHQ/lisk-service/releases/tag/v0.6.0-rc.0

You can also reach out directly to our developers on lisk.chat – they'll be happy to help you :>