Every day’s a school day. For others on the HA learning path:
To answer my own question, the above screenshots are from an add-on called Node-RED
Although the add-on says there’s nothing to do other than install and set a password, when attempting to use it, you’ll get a warning that the Node-RED companion is required. The install instructions are here. I couldn’t use HACS method of installing as it wouldn’t recognise the developer’s repository, so I followed the manual method.
The state node (as per OPs screenshot) is a trigger: state node.
HTH