How to add custom stages to RITMs but using catalog builder

[VaranAwesomenow]

Dear Team, am using Step based request fulfillment

flow in catalog builder and have built a catalog item, on RITM I see that the flow stages are as follows

 Service fulfillment process (Completed) , 

 Closed Incomplete (Skipped), 

 Completed (Completed)

Is it possible to make it more catalog item specific or add additional stages without having to customize the base flow Step based request fulfillment as this flow is read-only.