When adding a new connector, tab completion shows ssl as a valid attribute and the following command works:
/subsystem=web/connector=https:add(socket-binding=https,scheme=https,protocol="HTTP/1.1",secure=true,ssl={})

But read-resource does not show ssl anymore:
[standalone@localhost:9999 /] /subsystem=web/connector=https:read-resource(recursive=true)
{
"outcome" => "success",
"result" =>

{ "enable-lookups" => false, "enabled" => true, "max-post-size" => 2097152, "max-save-post-size" => 4096, "protocol" => "HTTP/1.1", "redirect-port" => 8443, "scheme" => "https", "secure" => true, "socket-binding" => "https", "virtual-server" => undefined }

}

Also, there is no way in the CLI to add/modify the attributes of ssl (like the certificate-key-file and password):
[standalone@localhost:9999 /] /subsystem=web/connector=https:write-attribute(name=ssl,value=

{"password"=>"changeit","certificate-key-file"=>".keystore"}

)
{
"outcome" => "failed",
"failure-description" => "No known attribute called ssl",
"rolled-back" => true
}