You can edit or remove the button's shortcode in Customize > Header > Header Text Area:
1. First you have to generate the button's shortcode using the Vamtam Beaver Builder (please check Guide to Vamtam Beaver Builder and How to save and re-use particular rows)
2. Next you have to create a Page Builder shortcode (please check https://kb.wpbeaverbuilder.com/article/192-use-shortcodes-in-your-layouts)
3. Last step is to add the saved row shortcode into the Header text area

or simply edit the demo shortcode:
DEMO CODE:
<a href="/janet-williams-appointments/" target="_self" class="vamtam-button accent1 hover-accent6 button-solid" role="button" style="font-size: 12px;"> <span class="vamtam-button-text">Book</span> </a>