Elisa uses a simple and practical layout beginning with one column in the first row and providing three columns in the second row.

In my humble opinion, Elisa would benefit from the option of a two columns view, for example: a tree file manager (sorted by album, artist, genre, or, as I suggested in another feature request, by directory) on the left and the playlist on the right. This way, there would be more space for the playlist.

As of now, the middle column takes up about 2/3 of Elisa’s window width. This is only practical for the large icons or large thumbnail view, such as the album or genre or artist view. In many cases, this column would not be needed at all; Elisa could utilize the left panel.

(My original feature request can be found here: https://bugs.kde.org/show_bug.cgi?id=468407. 
This request helps to split things up.)