ProNotes Markdown Plugin for Apple Notes
Mac Apps
If you have a lot of date saved in the default Apple Notes app and you aren't interested in migrating to Obsidian, Notion, Joplin or Evernote, you still don't have to settle for the limited formatting and back linking options you are provided. ProNotes, a free app, allows you to use standard Markdown syntax, if you choose to, in order to format your text.
You can also choose to use a floating toolbar with formatting tools. You can even use slash commands for titles, headings, code blocks, checklists, numbered lists and even tables.
Bi-directional links
macOS Sonoma introduced the ability to link to other notes. ProNotes allows you to view all notes linking to the current note via the Backlinks feature.