Okay after a bit of poking around I searched the jsons in the AppData\calibre\viewer\annots\ folder for "title" and got a list of jsons that contain bookmarks, but I can see no way of identifying which books they are actually from.
Example:
Code:
[{"pos": "epubcfi(/36/2/4/4/6/4/2/1:26)", "timestamp": "2020-07-09T02:37:45.983000+00:00", "pos_type": "epubcfi", "type": "last-read"}, {"pos": "epubcfi(/16/2/4/4/6/4/2/1:324)", "timestamp": "2020-05-25T16:08:04.585000+00:00", "pos_type": "epubcfi", "title": "Bookmark #1", "type": "bookmark"}]
However for the ones that are excerpts of text (rather than just "Bookmark #2" or whatever) I can search for those texts with Agent Ransack or Power Search and open the ePubs.
