I am using PlantUML API to generate Activity Diagram.
I have used GraphViz before and used rank parameter to define layout
rank=LR [for left to right]
I am trying to find similiar thing in PlantUML where I can change its orientation to "Left to Right" instead of existing layout i.e. "Top to Bottom".
You can use the following command with State, Class, Component or Usecase diagrams:
left to right direction
(see https://plantuml.com/use-case-diagram#d551e48d272b2b07)
Edit: This comment from 2012 originally claimed that the feature was scheduled for the next release. It's been available forever now.