Out of the box (OOTB) it is easy to do multiple properties and drive those based on a user selection, if you want to show data from multiple Things, you'll have to use the 'multiple datasources' option (I believe removing the check in Single Data Source). If you then use a Dynamic service, you can also switch up what Things are supplying data to the chart.
Thanks for the input. I know about the possibility you described. In my case, however, Things are dynamically added to the system, all of them sharing the same Thing Template. Your approach would work fine for a few Things, which are already connected. But how to dynamically bind a recently connected Thing to the Time Series Chart with the ability to display more of them at the same time?
I hope you understand my point.