Copy-drag not working with some elements on some systems
A recent discussion suggests that copy-drag is fully implemented on Windows, but my experiments show that copy-drag on the Mac is not well supported. Please bring MuseScore for Mac up to the level of Windows in this respect.
Also I'd recommend a different modifier key. I've heard that there are issues in MuseScore's IDE with cross-platform keyboard compatibility—maybe "uniqueness" is a better word.
Copy-drag on the mac is option-drag not command-shift-drag. This is true both currently and historically. It would be most helpful if MuseScore didn't stray from that.