As far as citations within markdown docs, pandoc-style citatations are the gold standard.
The idea is for Obsidian to directly handle anything in the form
[See @citekey, p 22-23] and variants (https://pandoc.org/demo/example19/Extension-citations.html).
The corresponding preview is generated using citeproc-js based on a .BIB file or CSL-JSON file (user maintained or software maintaned, by Zotero for example).
There should also be an extra pane for the bibbliography of the current file (or a Bibliography section at the bottom of the current file). Possibly, even a pop-up preview on each citation.
On broad strokes, this is essentially the approach that Zettlr follows.
Current workaround (optional)
Right now, there are a few plugins to work with citations. However, either they don’t use the pandoc format at all, or they provide some support of outputting [@citekey], but there’s no handling in preview (and they can’t because the API isn’t there yet).