If you need to have two different currencies, you can take this way to do it:
You need (at least) 2 users, and two groups.
For example, you create the users “Germany” and “Australia” and the groups “EURO Bills” and “AUD Bills”.
Optional, you can define the group “AUD Bills” as default for the user “Australia” and set the “restricted group usage” flag. With that flag set, the user “Australia” will not be able to see and do anything within any other group (except “All groups”).
Assign one currency to each USER. Then you assign a bill-template to each GROUP.
Now you can log in as user “Germany” and create bills in €, while each bill you create must be assigned to the group “Germany”, and the same with user “Australia” and the Group “AUD Bills”.
In the overview of bills, you can select the group “AUD Bills” and let Yabs show you the report for Australia, and the same for Germany.