In the System Modes section there are:-
1) Max / Blockchain - in max no transactions of address data is transmitted from the app. (Note you can still export and import via email becuase this app cannot control you email client.
2) Trader / Portfolio / Wallet - changing this setting changes the way the screens are organised to put emphasis on current price / current position or current transactions when you open the app.
3) Simple / Advanced - the trading mode allows you to use advanced mode; in advanced mode you may go into short positions, however the tax section is disabled in this mode.
This is because taxes when in short positions is far very complex and require specialist advice.
The coin selection screen is for selecting which coin(s) you are interested in.
The currency screen is for selecting your fiat currency, these use daily ECB rates. You can specify a custom currency outside the set defined the app with try to match the three letter currency code in order to resolve the rate.
If it cannot you can provide the EUR or USD rate, please note however you must keep the exchange rate up to date in this situation screen in order to get and accurate assesment of your liabilies.
The Exchange and Altcoin exchange are both used to get the currency mid price based on the last traded price, the historic prices are resloved using blockchain and cryptsy for Bitcoin and Altcoins respectively.
The tax settings configuration are covered here.
The final option here is to clear all data. It is recommended to export all transaction via raw export csv to email prior to doing this as a backup.
This export can be reimported afterwards.