Hello,
The plot (action) is something that allows you to define an action that characterizes some scenes. It is something that will allow you to highlight scenes whose actions are more or less related. This information is optional. It is not to be confused with the pitch, of the scenario mode, which is also a way of defining a scene in relation to what happens in it. With the pre-version 5.05.04 you have in addition the "step" element inspired by the book "The hero with a thousand faces" by Joseph Campbell.