Could you help me how to use distribute simulation in Ignition Gazebo?

Before using Ignition, interestingly I could find supporting 'Distributed Simulation' from the Ignition's main page.
https://ignitionrobotics.org/features

To check its implementation, I could find this keyword 'Distribute simulation across processes' from as below link and unfortunately it is indicated as '(coming up)' including other versions.
Citadel : https://ignitionrobotics.org/docs/citadel/comparison
Fortress : https://ignitionrobotics.org/docs/fortress/comparison

In my searching, I could find from 'Distributed Simulation' from 'Ignition Gazebo API Reference', but --distributed flag is not working.
The error message shows '/usr/lib/ruby/ignition/cmdgazebo6.rb:310:in `parse': invalid option: --distributed (OptionParser::InvalidOption)'.
Is there any way to use distribute simulation in Ignition Gazebo? I think that I can use more than 2 PCs in the Ignition Gazebo.
https://ignitionrobotics.org/api/gazebo/1.1/distributedsimulation.html

[Environments] Linux, Ignition-garden