This article will teach you how to streamline your Spotify playlists using the desktop and mobile apps.
This works best in the desktop app.
Here are those directions:
The process of merging playlists is nearly identical on Windows and Mac.

The screenshots below correspond to the Spotify app for Mac, but Windows-specific directions are noted where appropriate.
pop kick open the app and go for the playlist youd like to move songs from.
PressCmd+A(Mac) orCtrl+A(Windows) to select all songs in the playlist.

you might also hold downCmdorCtrlto select individual songs.
Right-smack the selection and chooseAdd to playlist.
Then, pick which playlist to copy the songs to, or selectNew playlistto make a new one.

Here’s how to do both:
TapYour Libraryat the bottom.
SelectPlaylistsand then fire up the playlist you want to copy songs from.
To transfer the whole playlist at once, tap thethree dotsunder the playlist name.

TapAdd to other playlistorAdd to playlist.
Select an existing playlist and then tapDone.
Or, chooseNew playlistat the top of the screen.

Enter a name for the playlist and tapCreateto copy the song to that new playlist.
Can You Add a Whole Playlist to Another Playlist on Spotify?
The web version works best for playing existing playlists andcreating new Spotify playlists.
Spotify will notify you if you’re copying songs that already exist in the merged playlist.
SelectAdd new oneson desktop orCancelon mobile to avoid duplicate songs when combining lists.
To remove duplicates after the fact manually, sort the playlist by title so you could easily find them.