投稿の途中にハイパーリンクを貼る方法はありますか？

[david (David Taylor)]

@merefield

is there any way I can do that from outside a post using a URL to point me to the post and the location within it

Yep, it works exactly the same way as within a post, just add the # at the end of the URL. For example:

https://meta.discourse.org/t/developer-s-guide-to-discourse-themes/93648#heading--4-b

https://meta.discourse.org/t/developer-s-guide-to-discourse-themes/93648#heading--4-b