Currently, sftp service is not in the default services list but net_connect probe gives the provision to add any service.
Go to Setup->Advanced->New , add the service name, port number and then you can use this service for the host.
SFTP port recommendations vary based on the vendor. Port 22, 1022, etc are some examples, so, it will be beneficial to contact your vendors if you do not know the port.
Environment
Release: CNMSPP99000-8.4-Unified Infrastructure Mgmt-Server Pack-- On Prem Component: