Last week we introduced a small change to editing app layouts that should make things easier. In the past if you needed to change the template that an app layout used you had to create a whole new layout. That's not a terrible thing, but it was a bit inconvenient.
We changed all that and made it so that when you edit an app layout you can now edit the template that the layout uses. When you change the template and click the "Save & Continue Editing" button the form will reload so that you will see the content blocks that the new template uses.