I managed to create a custom transcriber and use it in the assistant by setting the transcriber using an HTTP PATCH call to /assistant/ URL

curl -X PATCH https://api.vapi.ai/assistant/<assistant_id> \
  -H "Authorization: Bearer <public_key?" \
  -H "Content-Type: application/json" \
  -d '{
  "transcriber": {
    "provider": "custom-transcriber",
    "server": {
      "url": "<url of the transcriber>"
    }
  }
}'

Now, I'm creating new workflows but there I see each node can have different transcriber. I'd like to use my custom transcriber in my workflows as well, how do I do that? Thanks!

^^ This is correct. You can also review the API documentation to find the right formatting for the /workflows endpoint, but should be similar to /assistant endpoint regarding custom transcriber config.