I've been tracking this myself but good to have a reported bug for it since I haven't been able to fix it yet

Sorting by column in playlists works for me. Manjaro, juk 18.12.2. Drag and drop doesn't, though.

Git commit dc2d9c8e0fe64ff6059b0f5ca927ff338e7eeca4 by Michael Pyne.
Committed on 18/05/2019 at 04:27.
Pushed by mpyne into branch 'Applications/19.04'.

Add 'override' decl to fix compiler warnings, fix drag-and-drop.

This should shave off some 1,000+ warnings over the course of a build
with GCC 9.1.

This only addresses class declarations native to JuK, but Taglib and to
a lesser extent Qt5 moc still have (or generate) code that can result in
compiler warnings about suggested override declarations.

In the process I noticed that an existing drag-and-drop support function
(Playlist::decode) is no longer overriding Qt virtual functions, so it
has been turned into an auxiliary function to fix existing drag-and-drop
bugs from the KF5 port (tested by dropping files from Dolphin into a
playlist view).

Drag-and-drop from a playlist to another playlist (by dropping on the
playlist name) still remains broken for now.
FIXED-IN:19.04.2

M  +0    -5    collectionlist.cpp
M  +10   -10   collectionlist.h
M  +2    -2    coverdialog.cpp
M  +2    -2    coverinfo.cpp
M  +1    -1    deletedialog.h
M  +1    -1    directorylist.h
M  +2    -1    dynamicplaylist.cpp
M  +5    -5    dynamicplaylist.h
M  +2    -2    exampleoptions.h
M  +3    -3    filehandleproperties.h
M  +22   -22   filerenamer.h
M  +1    -1    filerenamerconfigdlg.h
M  +1    -1    filerenameroptions.h
M  +2    -2    folderplaylist.h
M  +5    -5    historyplaylist.h
M  +2    -2    juk-exception.h
M  +2    -2    juk.h
M  +1    -3    lyricswidget.h
M  +9    -9    nowplaying.h
M  +12   -15   playlist.cpp
M  +22   -23   playlist.h
M  +15   -15   playlistbox.h
M  +8    -8    playlistcollection.h
M  +1    -1    playlistitem.h
M  +2    -2    searchplaylist.h
M  +1    -1    searchwidget.h
M  +8    -8    slider.h
M  +1    -1    statuslabel.h
M  +6    -6    systemtray.h
M  +7    -7    tageditor.cpp
M  +1    -1    tageditor.h
M  +1    -1    tagguesserconfigdlg.h
M  +8    -8    tracksequenceiterator.h
M  +1    -1    treeviewitemplaylist.h
M  +9    -9    upcomingplaylist.h
M  +17   -12   viewmode.h
M  +2    -2    volumepopupbutton.h

https://invent.kde.org/kde/juk/commit/dc2d9c8e0fe64ff6059b0f5ca927ff338e7eeca4

Git commit 55a6bd7170e5b2ca6e9f826232574f2136a1648a by Michael Pyne.
Committed on 23/06/2019 at 19:13.
Pushed by mpyne into branch 'Applications/19.04'.

Fix drag-and-drop of playlist items onto a playlist icon.

This allows you to drag music tracks onto a different playlist, by
dropping the selected tracks onto the name of a different playlist.

There still seem to be other bugs (Dragging items onto play queue
doesn't enable play queue automatically; some playlists aren't properly
saved for some reason). But those will have to be fixed in other
commits.

FIXED-IN:19.04.3

M  +45   -2    playlistbox.cpp
M  +3    -0    playlistbox.h

https://invent.kde.org/kde/juk/commit/55a6bd7170e5b2ca6e9f826232574f2136a1648a

Thanks for the fixes.