Official comment
Sorry, unfortunately this isn't available within rekordbox. What I do, and even did with Serato, was to create a "History" playlist folder then store all my past mix histories as playlists within it.
With Serato, the folders are recursive, showing the contents of all playlists within, so you could basically see a list of ALL songs you've ever played. With rekordbox, until they provide that function, I create an "All Histories (Merged)" playlist at the top and then for every history playlist I add to that folder, I drag all the songs from the playlist to the Merged playlist to effectively do the same thing.