Tvheadend

I'm using Openelec 5.0.8 and Kodi 14.2. I have installed the TVHeadend Backend using the unofficial OpenElec Repo and the TVHeadend HTSP Client from Settings -> Addons -> Deactivated Addons -> PVR Clients. Live TV is enabled.

Via the Web Frontend, I've selected the pre defined list of Astra 19.2E and scanned the muxes and services.
Unfortunately (as I've read here - in german - http://www.kodinerds.net/index.php/Thread/24162-Fehlende-Sender-bei-TVheadend/) some channles are missing due to a frequency list that is not up-to-date.

I'd like to correct the frequency list but don't know where, as the folders mentioned in that post simply don't exist.
As quite some channles are affected I don't really want to add every single channel manually.