There is incidentally a very fresh topic w.r.t. manually linking a variant to an original: How do I link an edited JPEG as a variant of the original?
I think when using Photoshop/Camera RAW for RAW development, together with the “Develop RAW” menu entry, the resulting file should be properly associated with the RAW file. However, when using Lightroom, no .xmp sidecar gets generated for the RAW file and Lightroom instead just assumes a certain document ID for the RAW file. Unfortunately we don’t know the method for determining this document ID and thus cannot associate the resulting file with the RAW file.
I’m not sure about Photolab, but I’ll recheck how it behaves. Looking at the file name could actually be a good heuristic to make this work.