I have a function that outputs a nested array of messages. ie return [[message]]. This is so that all messages are sent on Output 1, which is a requirement since I have no control over the number of messages.
The problem I have is that the mqtt device I'm controlling (Tasmota) can't handle the flood of messages so I need to throttle them within node red. I tried the delay node, but that only throttled the array once, rather than throttling each message element within the array.
As thrashed out in the comments. The delay node has several modes, for this particular problem you need the "Limit rate to" mode.