https://github.com/protocolus/node-red-contrib-countula
This node loves to count! Ahh! Ahh! Ahh! This is a simple node that lets you view the number of msg objects seen since startup or when it was last reset. The Top output is just the msg object unaltered and the bottom output is just the count.
I use it to watch flows in the editor and to direct counts to dashboard nodes easily.