Merge lines in multiseries graph

[PavelNed]

Hi guys,

I am trying to make a panel with multiple vertical graphs, where each of these graphs can have one or multiple lines of data. Let's say first graph could be desired/present voltage over time, second desired/present current over time etc. 

Basically I am looking for a way how to use multi-series mode so that there is not a graph for each line, but for merged ones. My desired output should look something like this:

Any ideas how to do that?

Thanks for your answers.