Solution : https://service.sap.com/sap/support/notes/700700 (SAP Service marketplace login required)
Key words : 
project structure / wbs elements project editing mask            ->, faq 2-note 553661 wbs element number conversion            ->, master data / master data transactions, faq 2-note 569048 project editing mask            ->, faq 2-note 440186 customer specific fields            ->, faq 2-note 553832 ale-distribution create, faq 2-note line item reports 668514, project system solution basic areas, faq 2-note cost element reports 668513            ->, faq 2-note structure overview
Related Notes : 
       
| 702965 | FAQ 2: Project Planning Board | 
| 701077 | FAQ 2: PS Period End Closing | 
| 701076 | FAQ 2: Summarization in PS | 
| 701075 | FAQ 2: PS-Cashmanagement | 
| 700875 | FAQ 2: Structure Overview / Individual Overviews | 
| 700697 | FAQ 2: Logical Database PSJ, Selection in the PS Infosystem | 
| 700665 | FAQ 2: Planned Revenues from Sales Documents | 
| 678522 | FAQ 2: Data inconsistencies in the Project System | 
| 668514 | FAQ 2: Line item reports | 
| 668513 | FAQ 2: Cost element reports in Project System | 
| 668240 | FAQ 2: Hierarchy reports | 
| 579761 | OpenPS4MSP: FAQ note on OpenPS for Microsoft Project | 
| 573133 | FAQ 2: Call of network | 
| 573077 | FAQ 2: Archiving | 
| 570471 | FAQ 2: Confirmations in the Project System | 
| 570330 | FAQ 2: Customer-specific fields | 
| 569048 | FAQ 2: User status | 
| 554415 | FAQ 2: Authorization check | 
| 554139 | FAQ 2: Batch input | 
| 553832 | FAQ 2: Conversion | 
| 553661 | FAQ 2: Coding masks | 
| 545095 | FAQ 2: billing/accrual/quot./results analysis | 
| 440186 | FAQ 2: Validation and substitution in the project |