Editing a bookmark keyword should be made far simpler. The Keyword input box should be added to the "Add Bookmark" process, with some helper text to promote the feature, especially the custom search syntax.
Further to this, a keyword column should be added to the "Manage Bookmarks" Library editor. The only way (at least that I'm aware of) for a user to track down their active keyword for each bookmark, is to export and then parse the bookmark data file for the keyword key.
The only workaround I have for this, is to export all bookmarks and then parse them for the key "keyword". What we're needing is a keyword column to be added to the Bookmark Library, so we can easily see/sort any bookmarks with a keyword.