Other versions of this SDK (android, ios, php, javascript to name a few) support an extra argument to send additional data when reporting log, debug, warn, error, critical items.
In 3 different Flutter apps now, I have manually added the Android and iOS SDK directly and created a method channel to report items, instead of using the Flutter SDK. This is a lot of extra work. But I've done it because the interface in the Flutter SDK doesn't support additional data.
For example, something like
Rollbar.error(
message,
StackTrace.current,
{"foo": "bar"}
);
Please, please, please add this support