How can you tell that when an instance of node-red only knows about actions on one of the clients connected to the broker? For example, if you have a sensor publishing its values to MQTT then node red will be subscribed to that topic but will not publish to it.
First, this was meant as aspirational - beyond simple syntax and type checking - and MQTT was one example that came to mind.
I was assuming cases where both publishers and subscribers are within node-red. (Arguably, a bad assumption.) In any case, my MQTTInNode and MQTTOutNode instances would have "Topic" values (and mqtt-broker "Server" values) - and these could be inspected. Maybe all this does is surface typos on topic names.
My larger focus is on providing high (though configurable) guardrails to help "accidental coders" be more successful, more productive.