How we can create relation between two DWP Request? (Keeping the status of one request active until another request is not completed/closed using workflow)

The only way to relate Service Requests is through Dependent Service Requests. For example, requesting a RAM memory unit would not be possible without first submitting a request for a laptop.

Refer to the following documentation: https://docs.bmc.com/docs/display/dwp233/Specifying+dependent+services

Currently, there is no official mechanism to halt the fulfillment of a Service Request until the completion of another Service Request.