Piano Roll: adding button "Quick clone" (copying to the next beat)

Hello dear friends.

I'm very grateful you for that I can use such good DAW without copyright infringement or paying big money for this.

As very often I need to copy some highlighted area from one beat to the next one,
so I suggest to add such button, that will:
1. copy and paste notes from current beat to the next one (current - beat, in which the last touched (created, or just clicked) note is. (if no notes are highlighted);
2. copy and paste highlighted notes from current beat\beats to the next ones (if some notes are highlighted).

The button will appear in the last pattern, in which:
1. highlighted notes are present (if some notes are highlighted);
2. the last touched note is present (if no notes are highlighted).

Example:

Best regards,
Vladislav.

The issue names no files, tests, or entry points. Start by locating the Piano Roll UI and its note-selection and beat-copy behavior, then confirm the button placement and that both selected-note and last-touched-note cases work.

Written by the indexing model from the issue text.