Solution : https://service.sap.com/sap/support/notes/305856 (SAP Service marketplace login required)
Key words : 
additional key words sapscript, inserting clipboard texts deletes, entry-protected text lines, transfer protected text lines, choose goto -> change editor, insert -> text -> standard text, insert -> user clipboard, locked text lines, goto -> configure editor, sapscript pc editor
Related Notes : 
       
| 863113 | Locked text lines in PC editor can be deleted and changed | 
| 396958 | SAPscript: Inserting Clipboard deletes locked text lines | 
| 363243 | SAPscript: Collective note for template lines | 
| 337373 | SAPscript: copy locked texts to clipboard | 
| 302655 | SAPscript: Clipboard overwrites locked texts | 
| 302319 | SAPscript: Locked text lines can be edited | 
| 216488 | SAPscript: Incorrect format of locked rows | 
| 215591 | SAPscript: Deletion of locked lines in PC editor |