This is what a flexibility matrix looks like , where your Y axis depicts the main attributes of Project/Program and X axis displays the flexibility level.
Now lets see how it helps in Stakeholder Management
You as a Project or Program Manager, needs to do this exercise before the start of the Project.
Work with critical & impactful stakeholders and understand what are their flexibility levels on the three major areas, Scope, Time and Cost.
You need to align yourself , team and relevant process as per the ask from Stakeholders.
Please note : No stakeholder will say that he is extreme on all the three parameters.