Issue #552 on github requests sub-blocks within the .md file, but was closed without being implemented.
I suggest a simpler syntax for this:
+++
title = "Shard demo"
shard_marker = "-*-"
+++
Everything that goes here gets rendered out as normal and is available to the
templates as page.content
If a user doesn't opt in by specifying a shard_marker, everything else gets
rendered as normal and they wouldn't notice the feature.
-*- foo
The rendered html from this markdown is available to the templates as
page.shards.foo[0]
-*- foo
The rendered html from this markdown is available to the templates as
page.shards.foo[1]
-*- bar
The rendered html from this markdown is available to the templates as
page.shards.bar[0]
An initial rough implementation is available here.