Solution : https://service.sap.com/sap/support/notes/455473 (SAP Service marketplace login required)
Key words :
directory /specific/iscs/notes/note, nf menus default values- base key, report /nfm/conv_neb_to_default converts data, item proposal values / material master, sap cable solution solution, replace existing base keys, attached source code corrections, material master loses importance, existing default values remain, nf base keys