Reencode Destination to KV?

Given a key-value formatted source, routed through a pipeline where data is parsed into JSON then manipulatued, how do I write the new data back out in KV format? Using the filesystem Destination, I’m getting JSON after my pipeline regardless of whether I use Raw or JSON output. I’m assuming there’s a function I’m missing that does this. The closest thing I can find is Serialize, but that doesn’t support KV format.