Solution

[lukaskubanek]

I run into the same issue as described in this repository. The solution seems to be fairly simple, and you’ve partially pointed it out in the README. The trick is to set the draggingFormation on NSDraggingInfo in collection view’s draggingUpdated(:_) method after the call to super.

override func draggingUpdated(_ draggingInfo: NSDraggingInfo) -> NSDragOperation {
    let dragOperation = super.draggingEntered(draggingInfo)
    draggingInfo.draggingFormation = .none
    return dragOperation
}