i think it´s not supposed to be
If i Highlight with a Color something in a Webarchiv File, it is not shown up in the Annotations overview (CTRL+6) inside the Document.
Confusingly the Pictures are listed in the Annotations for Webarchives
But if i Highlight something in a PDF Document i can see it inside the File under Annotations Overview (CTRL+6) and it jumps easily between them.
I like the Annotation Feature, it´s like Bookmarking in a File.
This would be cool, but I’ve also just decided that converting a captured HTML page or web archive to PDF then adding my highlights is fine too.
I would love to figure out a way to read in my browser when I find something interesting, highlight right away (in the browser), then send that page to DEVONthink as a PDF with those annotations preserved, but I won’t hold me breath. Sounds like that’s far more difficult that it seems. Every app I’ve tried kills the annotations upon export to PDF. But I digress.
I am not sure that can be done to save a whole set of annotations on a page
But if you use Google Chrome then you can easily highlight one specific sentence or paragraph in a web page and save it as a Chrome Deep Link. You can save the Chrome Deep Link as a bookmark in DT3. The highlight will not be displayed with the built-in DT3 browser, but it will be displayed if you launch the URL from DT3 back to Chrome.