Add a "Universal" display setting to change multiple pages at once

You can already do that if you create your site using the dynamic CMS instead of creating a bunch of individual pages. This sort of thing is exactly why we created the dynamic CMS, so that you can use a single template and change the design and settings in one place, for one or all of your courses at once.

To create a setting that does what you are asking for individual landing pages would be next to impossible and pretty dangerous in terms of the impact of mistakes that you could make, so that's not something we will take on.

To learn more about the dynamic CMS and how to create membership sites using it, check out the support side documentation or OP University.