There are two ways to process a RAW image. One is to “develop it.” This is what Photoshop and Affinity Photo do. They take the RAW, give you some sliders and then the result is a new file (e.g., a TIFF) or a layer. You don’t go back to the RAW again.
The other way is what RAW Power, Nitro, C1, Lightroom, etc. all do. They decode the image when needed and you can adjust the RAW decoding at any point. If you decode with C1, unless you export a file (again, like a TIFF or a JPEG), there is nothing to give to Nitro, except the RAW file. And if it gets the RAW, Nitro will decode it (differently from C1). There is no way to convert a RAW, and then somehow keep it in a RAW format. It has to be converted into another format (as a new file), or decoded on the fly as Nitro and C1 do.