You can add bookmarks in a word document using the AddBookmark, AddBookmarkStart and AddBookmarkEnd methods. You can learn more about them from the Public Methods section in the below documentation link:
To make a bookmark to have text "ex novo", you may traverse C1Word's MainSection.Content to check if the current text is "RtfBookmarkStart" or "RtfBookmarkEnd" and then, add the text accordingly. A sample has been attached for your reference.
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