With work in https://issues.apache.org/jira/browse/BEAM-7760, Beam pipeline converted to DOT then rendered should mark user defined variables on edges.
With work in https://issues.apache.org/jira/browse/BEAM-7926, it might be redundant or confusing to render arbitrary random sample PCollection data on edges.
We'll also make sure edges in the graph corresponds to output -> input relationship in the user defined pipeline. Each edge is one output. If multiple down stream inputs take the same output, it should be rendered as one edge diverging into two instead of two edges.
For advanced interactivity highlight where each execution highlights the part of the pipeline really executed from the original pipeline, we'll also provide the support in beta.