Hello,
I haven’t upgraded yet, but from skipping through the version history it seems that the Alt+Click to quickly copy something to a different bar isn’t changed by Dorico 5. So no graphical preview or anything similar. (maybe someone can confirm this?)
If that’s the case: Would it be possible, to give Alt-Click the same graphical preview with the gray notes and the rhythmic grid as the Alt+drag with Live Editing? Because the preview of the Dragging looks really well designed, and so the users that still prefer not to drag notes could benefit from that preview.
You could make it that the preview only comes up as soon as the user moves his mouse, so there isn’t that much additional visual clutter (because the alt-key is part of quite a few key commands 
)
Best regards
Stephan