[opencms-dev] Search Index "Offline project"

[Roman Uhlig Maxity.de]

After always updating our OpenCms servers (starting from 6.0.x), we
installed a new one today with 7.5.1. After installation I noticed that
there is an offline project search index, which does not exist in our
updated installations (7.5.1 as well). I figure it's used for offline
search in the workplace?

My question: Is it possible to manually create this index or is that not
necessary/possible? I also noted a new rebuild mode option "offline".
What does that mean? "auto" and "manual" are quite self-explaining, but
I can't figure out that one. ;)

Thanks in advance,
Roman