"custom instructions" in Siri

Most of my use cases are adding notes while out driving or running.

Is it coming? I'm using "custom instructions" in a very general sense, somewhat related to setting it in ChatGPT or Perplexity AI or Phind, etc., but also in the broader sense of wanting to reliable guide the interactions. (Though admittedly many of my use cases may be well managed with Shortcuts triggering particular applications or workflows... But that requires some space and attention for foresight and foreknowledge.)