when creating the flow, you can define it as either process flow or screen flow. The first screenshot is screen flow where the flow action will be configured in assignment shape properties itself. Second screenshot is process flow where flow action will be configured in connector emerging from assignment shape.
create a flow rule, in the flow rule you see an assignment shape by default which is connect to the end shape or to the another shape. Double Click that connected shape and then you see your first screen shot of actions