satis wrote:

The article points out that substasks are absent, but it fails to point
out that recurring tasks are currently missing in action too -- which
for me means I can't replace my task app with it. To its credit it
supports the most common Markdown elements... but it isn't fully
Markdown compliant.

https://support.craft.do/hc/en-us/articles/360019555597-Markdown-Style-Shortcuts

You can open any task as a document and add tasks to the document, which are defect sub-tasks, although they don't show up in the task view, not sure why, because you can add due dates to these and even open them as docs too. I suspect this a bug or an unfinished feature.