Custom Template Tags

Hello!

My question concerns how you've created the correlation between certain page content and the template tags that are used in Header Elements. For instance, the {{post_title}} tag and the main page titles are connected, since that content is what appears in the header when we choose that tag. I'd like to make a tag that could pull from a certain content block on a page and display that content in the header. Is this functionality that GeneratePress has, or would you be able to recommend a method of doing this?

Thanks so much!