Moving songs while editing playlists doesn't work [#16733]

[MikeGahrns]

Repro steps:

Select playlist1, right click, Edit playlist
Select playlist2, right click, Edit playlist
With both playlists showing in their edit windows, select a song from playlist1 and drag it to playlist 2. Hold the Shift key, so that instead of a copy, the operation should be a move. The plus sign changes as expected, indicating that it should be a move, instead of a copy. But...

Result:
the song is added to playlist 2, but it still remains in playlist 1.

Note:
Copy works fine.

From previous bugs, I know that they was still some work going on with drag and drop, but I don't think that this issue was called out.
Also, still seeing that you can't drag and drop between different instances of MM5 to MM5. But dragging from MM4 to MM5 works. Getting drag and drop between MM5 and MM5 fixed is the killer feature that would really make MM5 shine for me, as it would really simply playlist management for those who spend a lot of time curating playlists.

[Lowlander]

I find now method to move files from 1 Playlist to another working. It also fails in the Media Tree and through Tabs. Cut & Paste is also not possible.

https://www.ventismedia.com/mantis/view.php?id=16733