For this:
GET https://<vsm-ip>/api/4.0/edges/<edgeId>/sslvpn/config/layout/
PUT https://<vsm-ip>/api/4.0/edges/<edgeId>/sslvpn/config/layout/
Use this:
GET https://<vsm-ip>/api/4.0/edges/<edgeId>/sslvpn/config/layout/portal/
PUT https://<vsm-ip>/api/4.0/edges/<edgeId>/sslvpn/config/layout/portal/
One more documentation issue that needs to be filed.