There used to be a feature whereby a bookmarked page could be flagged for offline use. Then when you visit that page, it instantly renders the page regardless of whether you are online. Was that removed?

There is a «File→Work Offline» tickbox, but that’s apparently something different because it gives no way to specify which pages should function offline.

You have to download it iirc. I'll check later tonight when I sit in front of my PC

Link: https://addons.mozilla.org/en-US/firefox/addon/single-file/

Downside: user needs to keep track of the downloaded files manually.

Unrelated upside: it preserves context better than printing a page to PDF.

I use SingleFile quite often. But it does not exactly provide the functionality I described.

It would be useful to tag a bookmarked page for offline access. That should simply be a toggle. The bookmark page would then be the UI for organising and controlling the offline content. From there, if I want a page to be organised in my file structure where it would then be reachable by other browsers, it would be useful to SingleFile offline pages while offline.