Using shortcodes in the Button text field
The Button text field is found at:
Button Settings > Content > Text > Button
Using shortcodes in the Button Link URL field
The Button Link URL field is found at:
Button Settings > Content > Link > Button Link URL
Example: The image above shows the use of the built-in "site_url" which generates the site's homepage URL. Once saved and viewed on the front-end, the shortcode will be processed and the result will be a button which links back to the site homepage.