Currently, in v6.4, we can only stack graphs from the same data set.

However, we can only set one base colour for a data set, so with a stacked graph, all the colours will be very similar.

Another issue is, that the order of the graphs in a stacked graph currently cannot be specified, at least not in an easy and intuitive way, and not at all if we use item patterns.

If we can stack the datasets too, then we can both specify the colours, and also the order of the graphs, if they respect the order of the data sets.