How do I add a new 1st root bookmark?

Q: I'm trying to add a new 1st bookmark - the first one.
AddRootBookmark just adds onto the end of current bookmarks.

Is there a way to "Insert at 0" sort of thing ?
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A: To insert a new root bookmark at index '0' you can obtain the root-
bookmark and then call root.AddPrev("First Bookmark").