FTP is not supported for VS recording. You can piece together FTP steps to develop a custom virtual service with the extension.
Please refer to this Communities Post which hopefully will help:
https://community.broadcom.com/communities/community-home/digestviewer/viewthread?MID=760765
https://community.broadcom.com/enterprisesoftware/communities/community-home/digestviewer/viewthread?GroupId=1843&MessageKey=a60ebcdb-e01a-4d72-9aa6-73c354cf6293&CommunityKey=94bda077-625b-4914-8ac3-c88a06c2cc23&tab=digestviewer
https://communities.ca.com/thread/241739216