Adding to playlists

[sherbs]

I'm trying to create a 'gym' playlist by listening to a shuffled 'all songs' playlist and adding to the gym playlist when I come across a track I want in there. However, everytime I add a track to the gym playlist, the all songs playlist resets. What setting do I need so that when adding a song from one playlist to another, the original playlist doesn't reset? I've tried various settings but nothing I've tried makes any difference.

Also, is there a way to prevent duplicates being added to a playlist?

Thanks.

[sherbs]

I found a button that lets me delete duplicates from playlists so that's sorted but now I'm really confused.

So far all my playlists have been in the Library so I tried making one in Folders to see if that worked any different, it didn't so I deleted it and went back to the Library. Now, when I tap 'add to playlist' I'm just shown a blank screen inviting me to create a playlist in Folders. How do I get the playlist I've been working on in the Library to show again?

Thanks.