When editing some The7 demos, you may also notice that footer and header areas are managed as a separate Elementor section marked with yellow (fig. 1):

Fig. 1. Footer template.

This is a footer/header template, it allows to create custom layout (which might be not available with theme tools) and edit it from one place: Dashboard -> Templates -> Theme Builder (fig. 2)

Fig. 2. Theme Builder.

You can edit existing templates here and create new ones in accordance with Elementor documentation. Templates are available for header, footer, content area and archives.