It would be great if we could view and edit a 'page master' without being able to see the rest of the clutter from the page so we can focus only on the items that will appear on every page.
You can save time from manually inserting the same elements across all your pages by utilizing the “Repeat on Some Pages” feature.
Once you finish designing an element, simply right-click on it and select the “Repeat on all Pages” option. You’ll be able to select on which pages the element will appear.
In order to only see the “master” elements, create a new blank page, and you will only see the “repeated master elements”.