Got it working, but it's not better than before...

wobuzz/ui/playlist.py

@@ -14,13 +14,15 @@ class PlaylistView(QTreeWidget):
     bold_font = QFont()
     bold_font.setBold(True)
 
-    def __init__(self, playlist, parent=None):
+    def __init__(self, playlist, dock, parent=None):
         super().__init__(parent)
 
         self.playlist = playlist
+        self.library_dock = dock
+
         self.app = playlist.app
 
-        playlist.view = self
+        playlist.views[id(dock)] = self
 
         self.setDragDropMode(QAbstractItemView.DragDropMode.InternalMove)
         self.setSelectionMode(QAbstractItemView.SelectionMode.ExtendedSelection)
@@ -39,7 +41,7 @@ class PlaylistView(QTreeWidget):
 
         self.setHeaderLabels(headers)
 
-        self.load_tracks()
+        #self.load_tracks()
 
         self.itemActivated.connect(self.on_track_activation)
 
@@ -141,6 +143,8 @@ class PlaylistView(QTreeWidget):
         if track:
             playlist_tabs.setTabIcon(index, self.playing_mark)  # mark this playlist
 
+            print(self.app.player.current_playlist.current_track_index)
+
             # mark the current track in this playlist
             item = self.topLevelItem(self.app.player.current_playlist.current_track_index)
             item.setIcon(0, self.playing_mark)