Solution : https://service.sap.com/sap/support/notes/387748 (SAP Service marketplace login required)
Key words : 
wbs elementor  goto -> capacity leveling -> total loadand, execute function  goto -> capacity leveling -> load, additional key words cj27, attached source code corrections, earliest wbs date, latest wbs date, capacity planning board, project planning board, function 'schedule', capacity requirements
Related Notes : 
       
| 381956 | Capacity overview in CJ2B: missing requirements |