Is your APFS encrypted volume is an external disk? I recommend you to use a symbolic link /Users/myusername/CS pointing to /Volumes/CS. Don't directly force mount the volume to your user home folder. It will damage the APFS volume.
Ensure your APFS-encrypted is mounted on your Mac, then run the following command below in Terminal to change its default mount point. ln -s /Volumes/CS /Users/myusername/CS
By the way, you should right-click to eject the APFS volume every time you want to stop using it rather than directly unplug it.