Thanks for the response. The CopyQ solution doesn’t do what I’m looking for (I don’t think, at least).
For example, I’d like to enter a snippet in a post (e.g. :slug:) and then whenever this is rendered, it renders the current content for this slug (which might contain markdown). If I change the content of this slug, then all posts using this would be immediately updated to have the new content (the post itself contains the slug only and the content is switched in upon render).
I’d be fine with the search not knowing the content exists too (and only showing the final cooked version is good for me).
Cheers