Thanks for the reply @Sahil Rangwala! I should have mentioned that I am using prefect 2.3 (though I've been using prefect since 0.11). The example you mentioned is in prefect v1 and it is exactly the pattern that I'm trying to avoid.
To be more specific, I have a very modular use case where a "controller" flow needs to kick off many "child" flows and eventually aggregate results in some way. The issue is we are building the modular "child" flows at a rapid pace and it is becoming burdensome to always go back and edit the "controller" flow when a new "child" flow is built.
I completely understand how to create subflows, but that is not what I'm after.
Is there some kind of pub/sub like pattern in prefect that would allow a "controller" flow to publish a request to "child" flows without knowing how many "child" flows might pick up the request? Then the "controller" would listen for results from all of the "child" flows until all of them complete and aggregate the data into a final result?