Solution : https://service.sap.com/sap/support/notes/661862 (SAP Service marketplace login required)
Key words :
componentcomponent type dtyp length decplacesrel_type_icon char6char 6 0then save, external reference /interpart link, change data type plm_document, cad relationship type, iconrelationship typeabbreviation icon_wri, implemented completely automatically, call transaction se11, call transaction se32, sym text164 rel, 'change' pushbutton