I found more tools from previous discussions:

https://tabnotes.page/

https://original.littr.me/

https://feather.wiki/

https://zareith.github.io/chillmd/

Although most tools use the "contenteditable" trick, I noticed some save the *entire page* as HTML. I used a different approach to enable downloading just the editable content:

  const blob = new Blob([content], { type: "text/html" });
  const url = URL.createObjectURL(blob);

I made one like this for myself. Love this. Mine has two panels. One for notes and the left side is just a tall menu, big buttons of my favorite sites/tools - saves a few clicks. Custom newtab is underrated.

I haven't really looked but my immediate reaction was - why an extension? Wouldn't a web page be capable of of this?