Tinboard is a client for Pinboard, based in the terminal, it includes:

• Add/edit/delete bookmarks.
• Various forms of filtering.
• Filtering with tags.
• Full text search.

Reddit thread where the Textual Markdown widget was announced.

Also includes the rather hilarious comment "I wish there were more full blown app examples out there", back when Textual was pretty damn new and barely out of the initial "CSS branch" release.