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ok, I think we should just replace SelectedRange by Dim in the next step
phhhh... trying to grasp the transition from SelectedRange. Need a var ref for dim. First thought to have distinct SelectedDim. But perhaps it all makes more sense to declare dims straight away with `vr.dim("name")`; this will tie the variable to the dimension. Disadvantages is we have to "pick up" all those dims from the graph.sources via pattern match... Let's see...
more like this? strip all the cruft.
dale; suggestion for the new API. "only needs to be implemented", harhar