Forcing orthogonal (vertical or horizontal) edges with dot

Your syntax seems correct. When I run it I get orthogonal edge routing (of sorts):

Which version do you have?

I ask because orthogonal edge routing is only available in Graphviz versions from September 28, 2010 and newer. Not all systems have more recent versions packed. On my system I had to download and manually install Graphviz to get a version newer than 2.26.3 (which is from January 26, 2010).

Assuming your actual graph contains more than 4 nodes, if you want the lines to have a bend and you don’t want to add extra (invisible) nodes, you should try playing around with the
graphs nodesep attribute. See code and image below.

digraph G {

    graph [splines=ortho, nodesep=1]
    node [shape=record]

    A -> {B, C} -> D
}