When I was building my first new songs, I kept trying to drag and drop the modules I wanted from existing songs. It felt natural to me to drag the intro from one song into my new one, drag the main beat from a different song into my new song, and so on. I kept doing that instinctively even though I knew that it didn’t work! I mention it because it was such and instinctive reflex, Perhaps a consideration in future software builds down the road…
What specific Drag&Drop functionality do you want?
I feel that simple Drag&Drop should move a song part from one song to another (same when holding Shift while dragging). Holding Ctrl while dragging should copy a song part. This is how standard Windows interface behaves. Is this the exact functionality you seek?
I was tempted to click and hold a part of a different song, say the intro, and drag that into my new song intro. It just seemed intuitive to me. I was thinking of my new song as a set of blocks assembled from existing songs.
To be honest I thought the functionality requested (which makes sense to me) is to be able to drag and drop songs from one folder to another without the need of exporting and importing. Dragging a song part to another song or part would also we useful rather than having find the required file and add it manually.