According to Middleman: Frontmatter, it is possible to access data defined in a page front matter inside ERB template under the current_page.data variable. However, this variable is not defined inside a Liquid template.
E.g.:
---
title: Hello World!
---
<h1>{{ current_page.data.title }}</h1>
yields an empty h1 tag.
Searching this problem, I found the issue #1202, but is seems to be about helper methods, which I believe to be a very different topic.
I also found Completed: Need Modules to allow exposing liquid variables. This one seems more relevant, but I don’t understand the solution. What is this page setting they are using? I see no mention about it in my http://localhost:4567/__middleman/config/.