We are introducing sections liquid tag and section groups

Themes

You can now create section groups in your theme’s layout. Section groups are JSON containers that allow merchants to add, remove, and reorder sections in areas of the layout file such as the header and footer.

To include a section group in a layout file, add the section group to the sections directory of your theme, then add a {% sections '<filename>' %} Liquid tag that references your new sections file to the layout file where you want it to be rendered.

To learn more, refer to section groups.