Separate names with a comma.
I don't know if this is a v18 host issue or a guest tools issue (still on v17 guest tools) but as soon as I upgraded to 18, my keyboard inputs are...
https://github.com/wegank/nixos-config/blob/7b89b4c6d1a87c83f10aa5d0f96fe0229795056e/hardware/parallels-unfree/prl-tools.patch Works for me on 5.18.