Graphviz: make edges not affecting the hierarchy of nodes

Question

I add edges (green) to graph, that makes hierarchy of nodes. How to add minor edges (red) that not affecting on the hierarchy?

Answer 1

You need {rank = same; <node names> }, e.g.

digraph G {
    a -> b
    a -> c
    c -> d
    c -> e
    a -> f
    c -> f
}

... gives:

... while

digraph G {
    a -> b
    a -> c
    c -> d
    c -> e
    a -> f
    c -> f
    { rank=same; c f }
}

... gives:

Answer 2

If you want an edge to not have an impact on ranking, you can simply set the constraint attribute to false:

If false, the edge is not used in ranking the nodes.

Example:

node1 -> node2 [constraint=false];