When dragging tracks from one playlist to another, the behavior is currently set to "Add," which creates duplicates. For my primary use case, I want to avoid duplicates and simply move tracks between playlists. To achieve this it's required to delete the track from the current playlist after adding it to the new playlist. This process is cumbersome, especially when handling multiple tracks, and increases the risk of errors, such as forgetting to delete a track or deleting the wrong one.
My proposal contains two parts:
1) Implement a shift modifier key to change the drag behaviour from "Add" to "Move", this method would be used for exceptions on the rule. [DONE

]
2) For my primary use case, allow users to switch the default behavior in preferences:
FROM:Add = Drag
Move = Shift + Drag
TO:Move = Drag
Add = Shift + Drag
This final step is important because constantly relying on a modifier remains cumbersome for someone who rarely uses "Add".
Together these two would greatly enhance efficiency and accommodate various playlist workflows, covering all preferred ways of using 'Add' and 'Move'.
Thank you for taking my request into consideration!