Perfect! Thank you very much, this answers my question and teaches me even more.
Your example not only explains how to achieve my desired layout but also reveals a little more to me about the config syntax. The config syntax does not appear to be documented anywhere. If you know of any reference to such a definition it would be very helpful indeed. For example I learned that the groups (rows) are automatically arranged in alphabetical order of their logical name, but the graphs with groups (rows) are arranged in the order listed in the config script. Hence I had to rename my groups to achieve the desired row order.
Now i have this:
The repetition of the syncrate chart is deliberate as part of the experiment.
Which gives this:
