To move items between collections, hold down Cmd (Mac) or Shift (Windows/Linux) when dragging items to the new collection. Remember that the “My Library” view always shows all items in your library, so you cannot “move” items out of this view.
(only sharing the link since you might find other relevant info. This isn't easy to find unless you know to look for it)
Nothing really to say other than that this definitely works. Note that you have to be dragging from an actual collection, not My Library, a search, or some other special view. While dragging, you should see the + sign near the cursor disappear and reappear as you press and release the Shift key, indicating whether it will copy or move.
OK got it. I think the problem is that I was moving from a subcollection to the collection itself - which is set to be nonrecursive and hence already contains the item. anyway, it now appears to work so sorry to bother you all. thanks for the help
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