Always prefer simulation_state or validation_state for "workflow state variable"
simulation_state and validation_state can be searched using
portal_catalog. It's preferred to use validation_state for documents with a
validation cycle and simulation_state for movements and deliveries. Note that
it's also important that 2 workflows with the same state variable are not used
for one document type. If you have to worklows with simulation_state, document
accessors like getSimulationState will not be able to determine which workflow
actually sets the simulation_state.