When do action runs that populate input fields?

I have an input field that's a string but is displayed as predefined answers which is dynamically populated using an action.

My question is when do these actions run?

What i'm trying to do is create a multi step workflow where the choices in the first step determine the drop down values in the second step.

As of right now, there's a default value in step 1 that's populated and when i change that to another value, the input in step 2 remains the same.

Is there a way to do this?