Currently there isn’t an export feature. I checked and thus requested for the feature to be added in one of my threads in the feature requests category.
As for documentation, I know that besides daily reports, I received a monthly summary that displays the position I closed and their results (total gain/loss for those positions) in one table and another table for positions that remain open (and thus there are no profits that are taxable as they are still just valuations/paper-money) followed by the account summary detailing all fees, deposits, withdrawals etc.
monthly statement really should be enough to do your calculations in regards to tax statements, but I can see the appeal in a single report that has done all the math for you (I just wouldn’t know if this would be by tax year or calendar year and whether it would come in time for filing taxes). I did request a profile section where these could be toggled/selected so you can control which of the reports you get as my email sees quite the sizeable influx of T212 emails in comparison to all my other senders. Currently seems you can only adjust the notifications if you spot the link at the bottom of the emails and not everyone does look at the fine print there xD