Hi Rajesh,
Nice question! Yes there is no option to export SEGW development. as an alternative, we have option to copy the project which will copy data model and service implementation. also we can take backup of code from DPC_EXT class methods. also we can download metadata of service so that we will be able to figure it out how Odata service was defined, entity type definition, relationship etc.
also we have option to save metadata out of query /sap/opu/odata/sap/<YOUR_ODATA_SERVICE_NAME>_SRV/$metadata to .edmx file and then we can import it to create new project which will recreate data model and service implementation from .edmx file.
I hope this help you.
Regards,
Chandra