The content editing system uses Liquid for dynamic content. See https://shopify.github.io/liquid/ for a basic introduction to Liquid.
To create a link to a page, you need to find the id of the target page. This can be found on the editorial view of the page.
To link to a page, using the title of the page as the link text:
{{ nodes['123e4567-e89b-12d3-a456-426655440000'].link_to }}
To link to a page using custom link text:
{{ 'My link text' | link_to_node: nodes['123e4567-e89b-12d3-a456-426655440000'] }}
To make a placeholder link:
{{ 'Coming soon' | placeholder_link }}