You are unable to make any changes to the five main workflow statuses in Karbon - Ready To Start, Planned, In Progress, Waiting, Complete.
Under each of these main statuses, you have the option to create and set your own customized sub-statuses to suit your firm's needs. You can then use the main statuses as a workflow guideline.
To apply the sub-statuses to your work, from the main menu:
Click on Settings > Workflow
Click on Work Types
Click on the <Work Type Name> that you want to apply it to
Check the box beside each of the sub-statuses you want to appear