When trying to use the default "duplicate line up/down" key bindings on Linux under GNOME (Manjaro), the input event wasn't making it all the way to VSCode.
Eventually, I found a discussion that suggested removing the bindings via dconf-editor[0], and that worked. These are the equvialent dconf
command-line invocations:
dconf write /org/gnome/desktop/wm/keybindings/move-to-workspace-up '@as []'
dconf write /org/gnome/desktop/wm/keybindings/move-to-workspace-down '@as []'
These can be restored to the default with: