Logic Pro recently changed the way it accepts drag and drop. If the ItemProvider contains UTType.midi, then Logic Pro shows visual feedback for the drop operation, but when the item is dropped, nothing happens. In the past, drag-and-drop used to work. With today's version (Logic Pro 11.2), the only way I was able to successfully drop MIDI was to provide UTType.fileURL and no other data types. But that's not a viable solution; I need other data types to be included too.
As a side note, I tested with Ableton Live 12 and it works with no issue.
Is this a bug in Logic Pro? What ItemProvider structure does Logic Pro expect to correctly receive the MIDI data?