By using the SharePoint object model, you can add your own workflow
status that appears in the workflow association column. Each workflow
status value corresponds to an integer that represents its place in a
zero-based ordered list of column values. The first 15 values in the
Microsoft.SharePoint.Workflow.SPWorkflowStatus enumeration are
reserved by Windows SharePoint Services for internal use.
To add a custom status value, define a new StatusColumn element under
ExtendedStatusColumnValues in Workflow.xml. The first status column
value you specify is assigned the integer value of 15; the second
status value, 16; and so on.
You can see more details here.
if you would like to extend the workflow statuses enumeration you can try to use this approach.