You could ofcourse adapt the value of an variable, save the m-script and then run it again. That will overwrite your simulationplot with a new result.
There is another way to simulate for various values of an variable. See movie (approx 30 seconds).
Main idea is: Right click on the value of your variable and select "Increment Value and Run section". It requires that the whole simulation you want to do is within an section. (Sections or cells can be created with %% Name section)