Quick notes duplication in the Piano Roll

I frequently find myself doing one tedious task: copying a bunch of notes and moving them so that the head of the newly created group touches the tail of the previously present notes.

I wish a quick Ctrl+D hotkey could do this for me, it'd save me a lot of Piano-Roll time.

What do you think?

Also: same functionality for Song Editor would rock even more (but not without the ability to remove multiple selected clips at once with Delete key).

Start by locating the Piano Roll and Song Editor keyboard-action entry points, then inspect how selected notes or clips are represented and how existing copy, move, and delete actions behave. Done means Ctrl+D duplicates selected Piano-Roll notes directly after the existing notes; any Song Editor support should also include deleting multiple selected clips with Delete.

Written by the indexing model from the issue text.