maybe you need play with CLI a bit; everything is documented under 6.0 CLI guide in docs.fortinet.com.
It seems a typo error, is 'ldb-method' and not 'lbd-..."
Use '?' in each command instance, and you'll can see which options are available.
config firewall vip
set type server-load-balance
set server-type http
and you'll see:
id Custom defined ID.
uuid Universally Unique Identifier (UUID; automatically assigned but can be manually reset).
type Configure a static NAT, load balance, server load balance, DNS translation, or FQDN VIP.
ldb-method Method used to distribute sessions to real servers.
src-filter Source address filter. Each address must be either an IP/subnet (x.x.x.x/n) or a range (x.x.x.x-y.y.y.y). Separate addresses with spaces.
extip IP address or address range on the external interface that you want to map to an address or address range on the destination network.
*extintf Interface connected to the source network that receives the packets that will be forwarded to the destination network.
arp-reply Enable to respond to ARP requests for this virtual IP address. Enabled by default.
*server-type Protocol to be load balanced by the virtual server (also called the server load balance virtual IP).
persistence Configure how to make sure that clients connect to the same server every time they make a request that is part of the same session.
nat-source-vip Enable/disable forcing the source NAT mapped IP to the external IP for all traffic.
*extport Incoming port number range that you want to map to a port number range on the destination network.
gratuitous-arp-interval Enable to have the VIP send gratuitous ARPs. 0=disabled. Set from 5 up to 8640000 seconds to enable.
srcintf-filter Interfaces to which the VIP applies. Separate the names with spaces.
http-multiplex Enable/disable HTTP multiplexing.
http-ip-header For HTTP multiplexing, enable to add the original client IP address in the XForwarded-For HTTP header.
monitor Name of the health check monitor to use when polling to determine a virtual server's connectivity status.
max-embryonic-connections Maximum number of incomplete connections.
color Color of icon on the GUI.
The options beginning with '*' are mandatories
Hope it helps