I spent more time that care to admit trying to setup a shared folder between my windows host and Kali VirtualBox VM. So hopefully the Google algos pick this one up and save you the time trying to find the right packages to fix this a clipboard sync.

apt-get update
apt-get install -y virtualbox-guest-x11

Go for a quick reboot once the above commands are complete and you should have clipboard sync (text) and shared folders should mount successfully.

More Linux Tidbits: