Perhaps I should make a tutorial on how to create your own custom formatters for App Connect.
Here a very simple one for base64 encoding:
dmx.Formatters('string', {
encodeBase64: btoa,
decodeBase64: atob
});
Usage:
{{ 'Hello world'.encodeBase64() }}
becomes SGVsbG8gd29ybGQ=
{{ 'SGVsbG8gd29ybGQ='.decodeBase64() }}
becomes Hello world