AbaNinja provides automatic conversion rates for the foreign currencies Euro (EUR) and US Dollar (USD). With a paid subscription you have the possibility to enter manual conversion rates in different currencies.
The exchange rates, which are stored under Settings > Accounting > Currency, are updated once a week via an interface to the European Central Bank.
If you do not want to use the automatic exchange rates but want to enter your own rates, this can be changed under Settings > Accounting > Currency by deactivating "Automatic exchange rates".
This functionality is part of a paid subscription that you can purchase via the Swiss21 portal.