<div class="mw-collapsible mw-collapsed" id="mw-customcollapsible-myTable"> {content}</div> <div class="mw-customtoggle-myTable wds-button wds-is-secondary">Show/Hide</div>
wds-button wds-is-secondary is the class for that type of button.
wds-button wds-is-secondary
What do you think?