Another option would be to keep track of all the buttons in each 'page' of settings (maybe through a struct or something similar) and toggle the visibility of those ui objects based on which page of settings you are currently utilizing.
For example, to set a button called Button to be invisible, you can use the following line of code:
app.Button.Visible = 'off';
This will be easier than actually clearing all of the buttons each time, since all of the callbacks and other functionality will remain, they will just be invisible. When you want the button to appear again, you can just set the visible property back to 'on:
app.Button.Visible = 'on';
