There could be a checkbox on units that allows you to define them as a breakpoint.
When flow reaches that unit, the Unity editor would pause until you unpause it manually.
That would basically do what I was looking for.
In PlayMaker you right-click then select "Toggle Breakpoint" which adds a breakpoint indicator and will pause the editor once you reach that state. That's what I tried to do just now in bolt out of habit.
Fear not, this is planned for a future version! Currently scheduled at v.1.6 on the roadmap.
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