Looking over the README, it looks like the following is an issue when users have HTML image headers in their markdown.
$ npx markdown-notes-tree **/*.md
Processing files in order to build notes tree
Error: No title found for Markdown file /path/to/docs-as-code/playbooks/general/incident-severity-scale.md
$ head -4 general/incident-severity-scale.md
<img width="100" src="../../assets/images/sammy-heart.png" alt="Sammy Love"
align="right">
# Incident Severity Scale
It would be awesome if there was actual markdown parsing to allow for image headers.