Following up…
Obsidian just works on my Org-roam directly (powered by Md-roam; I only have .md files).
Thanks for mentioning Obsidian; never thought of trying it out without this post.
Its capability and underlining logic to detect links for markdown files are a superset of Md-roam – even sub-directories and the the pandoc syntax of [@citation-key] as part of “Unlinked mentions”.
Looks like I can use Emacs for better editing experience (for me, Emacs key-binding of text navigation is natural), and use Obsidian for exploring my knowledge graph…