I’ve had a quick look at the code, there doesn’t seem to be a way to change the “default” currencies, they are hardcoded. See https://invent.kde.org/frameworks/kunitconversion/-/blob/master/src/currency.cpp and search for “addCommonUnit” and “addDefaultUnit”.

You can specify your target (e.g. 11 USD in INR should work), however I don’t know how to change the defaults or if KRunner is “smart” enough to automatically include INR in those conversions.