There is no template available to migrate WBS (Work Breakdown Structure) element.
SAP S/4HANA Cloud
It is not possible to migrate WBS elements to S/4HANA Cloud - this is not supported.
The project concept in on premise ERP and SAP S/4HANA Cloud are different. For further details, refer to SAP Knowledge Base Article (KBA) 2596400.
For a list of available Migration objects, refer to the following link: Migration Objects for SAP S/4HANA Cloud - Available Migration Objects
There is also a possibility to request new features in migration content. For more information, refer to KBA 2676589 - Request for new features in SAP S/4HANA Data Migration Content
Migrate Project, PSP, WBS-element , KBA , CA-GTF-MIG , SAP S/4HANA Data Migration Cockpit Content (LTMC) , Product Enhancement