There are ways to start a flow from Powerapps, passing parameters.
It's a shame we don't have the same for starting flows from within flows.
This would make it really easy to start using flows as "functions" that can be reused.
Currently, I find myself reproducing parts of flows in several "copies" of the flow.
A (simple) example?
Suppose I create a logging SP list for seeing all the changes some of my important flows actually perform (this could be for debugging or for other reasons). I have to reproduce all the parameters of this "create item" step time and again, while I would love to just abstract it away in a flow called log_entry that I just pass some parameters to (the actual info to log).
Obviously this has the added advantage of better maintainability (if there is an error in my logic or if I want to change the way it works, I just have to make the change in one place).