When you work with multiple currencies, you should keep a separate Book for each currency you work with.
How you operate will depend on your business processes, regulations and local rules and reality.
Some uses intermediaries and track fees, taxes, spread etc. Others simply record transactions on both both books when sending remittances, then track gain/losses of exchange variation once a month.
No matter your process, you will need one book for each currency.
Simple transfer example
Here is a very simple example of a remittance operation from Brazil to USA:
Book 1 (BRL)
The US Operation account is an asset.
Book 2 (USD)
The Brazilian Operation account is a liability.
In the above case we sent money from Brazil to USA operation, and kept the balance as an Asset for Brazil and a Liability for USA. You can later pay the Brazilian operation back, and/or clear the remaining balance as an Outgoing Expense or Incoming Revenue, depending on cambial variations.
This is a very simplistic example that reflects a given process. Yours can totally differ from it.
You can aggregate the Balance Sheet and Profit & Loss statements using Google Sheets Add-on.
Tracking gains and losses of exchange variation
If you track balances of accounts in multiple currencies, the currency rates varies over time, and, depending on the scenario, you gain or loose money over the balances in one currency, compared to other.
To periodically track those gain/losses, you can fetch relevant balances of each account with the Google Sheet Add-on for Bkper to one Google Sheet calculate the balance represented in the other currency with the formula =GoogleFinance("CURRENCY:USDEUR") and record back to the book as an Income or Outgoing expense:
This can be a quite laborious process, specially if you are dealing with many multiple transfers and accounts. In that case, you can automate the whole process by using Bots.