In the regular . Cs source file that stands behind the page where the AppBar is placed.
Presumably the "favourites" button performs an action on the currently selected/displayed item on each of the different pages. As the action is specific to each page you'll need to have something on that page to handle the button click.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.