In order to use this you'll need to do two things: Firstly enable Siri support for Kanbann on your *phone*, by saying "Hey Siri, Create a note Testing 321 in Kanbann" and tapping "Yes" (this is a one-time thing).
Create Trello cards using Siri on your watch: "Hey Siri, Create a note Testing 321 in Kanbann".
Secondly on your *watch* you need to designate the default list for new cards by navigating to a list, hard-pressing the screen, and tapping the "Set as default..." button.
Kanbann brings Trello to your Apple Watch.
Kanbann is in no way associated with Trello or Atlassian.