Option 1: Shortcode
layouts/shortcodes/rawhtml.html
{{ .Inner }}
markdown
{{< rawhtml >}}
<ol reversed>
<li>Foo</li>
<li>Bar</li>
<li>Baz</li>
</ol>
{{< /rawhtml >}}
Option 2: Attribute
config,toml
[markup.goldmark.parser.attribute]
block = true
markdown
1. Foo
1. Bar
1. Baz
{reversed="reversed"}