Just like with VST instruments, it would be really great to have a Remote Control Editor for the Sampler track, as well as specific methods in the MIDI Remote API for scripting operations. The Sampler could use a bit more attention in this regard.
The XML once saved will be in a directory under Documents/VST XMLs with the name D1B42E80F1124DFEAFEDE2480EFB4298. It won’t be under the vendors directory.
You can use the same approach for the Drum track type.
That being said, I don’t actually see all this usable when it comes to controlling the sample using the normal Instrument→Parameter binding. I do have a workaround using DirectAccess, perhaps I will upload a snippet.