Hi Donaldo,
I'm am not 100% sure of your current set up.
I will put you out of your misery regarding the visual administrator. For 7.3/4 systems there is none, all configuration is done via NWA.
You have a java system (portal) but from what I have gathered it might use an ABAP stack as its user store, this would explain why you see no ldap in the drop down. (its possible to change it to ldap but its not supported).
You still can use spnego so your window users can login via SSO, you can map the LDAP users to users on the back end via attribute mapping. There is no step by step documentation for your version unfortunately. The documentation for the older release will help:
Configuring SPNego with ABAP datasource | SCN
But remember there is no VA. All you have to do on the this java stack is to pick attriubette for the user mapping tab in the spnego wizard. Then use the above guide to help you understand how it works.
I hope this helps.
Kind regards,
Cathal.