Manually Set an Item as Active Any item can be set to active to indicate that the page is anchored to the respective section.
Important Notes: When using plain HTML to make a Table Of Contents have a default active section, add a c-bolt-toc__item--current class to the desired Table of Content item.
Demo
Twig
{% set toc_items %}
  {% include '@bolt-components-toc/toc-item.twig' with {
    text: 'Section One',
    url: '#section-one',
  } only %}
  {% include '@bolt-components-toc/toc-item.twig' with {
    text: 'Section Two',
    url: '#section-two',
    active: true
  } only %}
  {% include '@bolt-components-toc/toc-item.twig' with {
    text: 'Section Three',
    url: '#section-three',
  } only %}
{% endset %}
{% include '@bolt-components-toc/toc.twig' with {
  content: toc_items
} only %}
HTML
<div class="c-bolt-toc">
  <nav aria-label="Table of Contents">
    <h2 class="c-bolt-toc__header c-bolt-toc__header--hidden">
      Table of Contents
    </h2>
    <ul class="c-bolt-toc__list">
      <li>
        <a href="#section-one" class="c-bolt-toc__item">
          Section One
        </a>
      </li>
      <li>
        <a href="#section-two" class="c-bolt-toc__item c-bolt-toc__item--current">
          Section Two
        </a>
      </li>
      <li>
        <a href="#section-three" class="c-bolt-toc__item">
          Section Three
        </a>
      </li>
    </ul>
  </nav>
</div>