Can not limit up-/download in Sync-Client (Kubuntu)

I can not limit the up-/download in Sync-Client (Kubuntu). The setting is in the sync client, but everything is greyed out. I had a look in the config file. The config-file does not contain any entries relating to up-/download. I am hoping that adding those entries to the config-file could fix it. Unfortunately I could not find any samples on the web. So can somebody provide we with a config-file or the missing entries which relate to the up-/download settings? Any other suggestions which could help me fix this are also appreciated.

It’s a similar issue here: Windows Desktop Sync Bandwidth Limit Issue

Similar, but I am not sure if they are related.

That’s true, but the workaround I proposed is the same, also further debugging with the original owncloud client.