Solution : https://service.sap.com/sap/support/notes/322427 (SAP Service marketplace login required)
Key words : 
'spras' -> select 'insert line' -> enter field, generated character string formed, sapscript function module open_form, document title displayed consists, attached correction instructions describe, nast-kappl output type, function module open_form, field itcpo-tdtitle, field lvs_itcpo-tdtitle, choose 'change' select
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