You can find Lightmass Portal in All Classes tab. The best thing about UE 4.11 preview 1 is that I don’t need to mess around with baselightmass.ini file anymore. In Lightmass setting, I rarely use high indirect bounce values, mostly around 10-30. Using low light scale such as below 0.5 also won’t tax light building as high as in previous versions. Thanks to Intel Embree integration. It really helps and makes light building much, much faster.
However, don’t use UE 4.11 preview 1 for your real project yet. The official release of UE 4.11 is February 2016.