Please see Creating a custom workflow process in the official documentation.
Enterprise customers needing to create a custom workflow should contact Magnolia support first.
Please also note that the Magnolia incubator is already providing many extended features:
- Six Eye Workflow (adds a second configurable approval layer)
- Eight Eye Workflow (adds a third configurable approval layer)
- Task Email Notifications (sends emails without customzing workflow)
- Publication Task Config (route approval to different groups based on path and workspace).
All of these modules can be mixed and matched and used together.