From here: https://www.whonix.org/wiki/VirtualBox_Guest_Additions
For Whonix-Gateway, one directional clipboard sharing from host to Whonix-Gateway is enabled and secure.
Clipboard sharing in GUI Gateway works. But how can I paste from Host to Guest in non-GUI Gateway?
What I usually do is turning on GUI in Gateway and edit (pasting) in Tor config file. If clipboard sharing works in commandline environment that would be more convenient to work with.