I do not have a plus button to add songs to playlists.

[BaguetteAndButter]

I do not have a plus button to add songs to playlists. I can use the 3 dots to add to a playlist I have created, but I cannot add to the playlists that have been shared with me. Other people can add to the shared playlist but I can't.

[AlejaR]

Hey @BaguetteAndButter,

Thanks for posting in the Community and welcome. 

We’re always testing possible improvements, so you or someone else may see something new or get a limited feature temporarily on the app. This could be the reason why you can see the (+) plus button. You can read more about it here.

That being said, if you can see the heart button 💚, you can continue using it and continue adding new songs to your playlists by selecting the option in the three-dot menu. We'd recommend to maintain the app up-to-date, so you won't miss any further developments. 

On another note, just to confirm, did you mean that you joined a collaborative playlist, but you can't add songs? If a friend share a playlist with you, but the link they sent is not an invitation to be a collaborator, you won't be able to add songs to it. 

Hope this clears things up. Keep us in the loop!