Thanks Adam,
Just before your reaction I found out that indeed I had to turn on Automatic Mode and turn off Show Animation, because I prefer to have the same structure in the right column of the Timeline as in the OM.
The problem occurred, because I probably chose “Show tracks” with a right click on one of the objects in the OM; after that the Timeline turns empty and Automatic Mode is turned off.
Anyway, I’m on track again. The benefit of having the option to choose the same commands on different places within C4D (with sometimes slightly different results) turns into a little nightmare for a beginner.