This is a simple candlestick downloading app based on Oanda's REST API. It is designed to do the one job and that is to download candlestick data in a CSV format. You can specify the date range, granularity, and the instrument. You need to provide your Oanda API key in order to use this app.
Warning The app is available only for macOS.
This app integrates well with FXTester. You can import downloaded data into FXTester. Given the fact that it produces rather easy format to modify - you can also use it to download data for your own custom backtesting app.