Youtube How To Make Duplicate Entries On Playlists

I'm sorry to put this here, but I have web searched 12 different ways & all i get is how to make a playlist or how to remove duplicates.
I haven't been able to add a title more than once to the same playlist since they changed the site., but I see that at least one channel has repeats of their newer vids, & somehow I accidentally put 2 of teh same vid on one of my playlists yesterday. Anybody know how I can do this unpurpose??'
Thanks.