Thanks for taking the lead on this!
Could this appear on the side of topics, like how infoboxes typically appear on the right side?
Looks like the example I originally gave for Obsidian required a Multi-Column Markdown plugin as a prerequisite.
Discourse’s built-in table CSS is not so bad other than it can’t appear on the side of a topic. Getting flexibility in the layout on the page and within the box is probably the biggest hurdle.