Marginer

Highlight any page, add notes and emoji, export as markdown.

Bookmarklet

Show your bookmarks bar (⌘⇧B / Ctrl+Shift+B).
Drag this button onto it: ✍️ Marginer
Open any page and click the bookmark. Click it again to collapse.

Userscript — adds the "this page has notes" indicator

A bookmarklet can't tell you a page is already annotated: nothing of it runs until you click it. With Tampermonkey or Violentmonkey installed, Install the userscript and revisiting an annotated page brings your highlights back on its own, with a small pill in the corner showing the count. Press ⌘⇧U / Ctrl+Shift+U to open it anywhere else.

It reads the same storage as the bookmarklet, so you can install both.

Which one?

	Bookmarklet	Userscript	Extension
Install	drag a link	needs Tampermonkey	load unpacked
Shows a page has notes	no	yes	on click
Works on strict-CSP sites	often not	yes	yes
Notes stored in	site localStorage	site localStorage	chrome.storage

Notes are keyed by URL and never leave your browser.