SSL-VPN Portal selection

I may be missing something, but it seems like the only way to direct users to certain SSL-VPN portals is via the Authentication/Portal Mapping section in the SSL-VPN Settings.  That entails creating a user group on the Fortigate, then mapping that group to the desired portal.  

I'm wondering whether it's possible to have the user select which portal to access.  With the Cisco Anyconnect, we could publish different "group policies" (portals) via different URLs - like vpn.company.com/portalA and vpn.company.com/portalB.

Is there a way to have the users decide which portal they want to connect to?  The alternative will be to move user accounts in and out of user groups as necessary, which isn't ideal.