Can not add to a Playlist

I can see and play from my play Playlists (see some of them on my Screenshot below). But I can not add tracks or albums to my Playlists (see another Screenshot). I does not matter if the music is on my hardrive or from Tidal, I cannot add them to my Playlists.
Just found out, if I make a new Playlist, I can add music to this Playlist, but not to the old Playlists

Are the playlists you cannot add to ones you imported (such as m3u) or are they ones you created in Roon?

They are created inside Roon

Still the same issue with the playlists. I can see my old playlist, and can play them. BUT I cannot add music to the old playlists. I can make a new playlist and add music to it. But I want to add music to my old playlists. Am I the only one having this issue?