Didn't realize that existed. But it seems to only allow for one bookmark, if you mark a position in file A, and later find yourself wanting to mark a position in file B, the file A bookmark must be replaced with the file B bookmark, which limits its usefulness. Also it seems to not be retained across executions.
I think what I had in mind was having the 'library' track where I left off in various podcasts and audiobooks, so any particular file I set a bookmark on, could be resumed from. Like multiple files at a time, and across reboots, etc.
Anyways, enjoy the holidays!