New Sections Not Showing Up in Shopify Theme Customizer! How to Fix

The newly created section shows on the Shopify theme customizer only if we set presets in the schema. We have to add a preset name and category into the schema of the new section. A sample schema is given below.

{% schema %}
{
  "name": "My New Section",
  "settings": [

  ],
  "presets": [{
    "name": "My New Section",
    "category": "Text"
  }]
}
{% endschema %}

Presets are required only for showing the sections on the home page "Add section" list. For use in any template file, we can directly add the section as  {% section 'my-new-section' %}. Here my-new-section is the section file name.

Explore more about schema presets in Shopify Documentation