Symlink for the shared folder from the guest machine is disabled by default, you can enable it with the following command from the host. My OS on the host computer is windows, so it would be like:
C:\Program Files\Oracle\VirtualBox\VBoxManage.exe setextradata VM_NAME VBoxInternal2/SharedFoldersEnableSymlinksCreate/SHARED_FOLDER_NAME 1
Where 'C:\Program Files\Oracle\VirtualBox' is the installation location of VirtualBox, 'VM_NAME' is my virtual machine name, and 'SHARED_FOLDER_NAME' is the name of the shared folder in the host machine.
If you are using Linux on your host, you can use the same command as below:
VBoxManage setextradata VM_NAME VBoxInternal2/SharedFoldersEnableSymlinksCreate/SHARED_FOLDER_NAME 1
Remember it is required to shut down all running virtual machines and close the VirtualBox before execution of the commands. After that windows users run it as an administrator privilege (right click on Virtualbox and run as admin). Now you can create a symlink in a regular way:
ln -sv /to/source/directory /to/destination/directory