Since Buttonizer v2.2.4 it's possible to select pages and blog posts as button action.
What's the different between
Website URL action?
When you select a page, your button will always redirect to the corrosponding URL of the selected page, even if you change the slug or path of that page. The URL of the button will change automatically for you without any further action.
Website URL action, you need to update the URL by yourself after each change. We recommend using this feature if you want to link to external websites, such as documents.